When concentration and awareness are working together, for a fraction of a second you may have a taste of what enlightenment might be. You might find yourself with no discursive thoughts. When you discover that your unwholesome discursive thoughts have been pacified and subjugated, there might be a gap. A pure gap of the absolute, ideal state of mind might occur to you. For everyone, without exception, such a glimpse is always possible. You realize that bodhichitta, or awakened heart, is not a theory or a metaphysical concept, but a reality. It is more than rain clouds gathering in the sky—it is the actual rain.
From “A Glimpse of Wakefulness” in The Profound Treasury of the Ocean of Dharma, Volume Two: The Bodhisattva Path of Wisdom and Compassion, page 6.
Throughout the early 70s, Chogyam Trungpa began to give public meditation instruction - he often referred to it as 'shamatha-vipashyana', which he also referred to as calm-abiding/clear-seeing or mindfulness/awareness. This instruction was in many ways similar to the standard way of techning shamatha, it had many common concepts - but from very early on he wanted to show people a glimpse of what he called the 'gap'. He wanted people to glimpse 'the fourth time', and grow from that glimpse into genuine realization of nonduality, selflessness, egolessness, mahamudra, dzogchen - whatever you want to call it. He did not 'zap' people with pointing out instruction from day one but but emphasis on discipline and working from the ground up ina down to earth way. He was very concious of his audience, namely - hippies! His talks were hippy galore and he was very cautious about how to frame the teahcings lest they made a big deal about it and turned it into 'golden chains'.
Another note I'd like to mention is that when I say 'Mahamudra View' - you can pretty much replace the word 'mahamudra' with several others, ati/annutara/unborn/EVAM/dzogchen/open/space/etc. Chogyam Trungpa was trained by great teachers such as Khenpo Ghangshar, Dilgo Khyentse, Jamgon Kongrtul so he was non-sectarian and seemed to hold gthe same view that experience is paramount, and that ultimately the experience of mahamudra/dzogchen are pointing at the same moon. Mahamudra and Dzogchen are both describing the same flower in slightly different dialects as far as we're concerned.
"Khenpo Gangshar does not give a complete presentation of the instructions on mahamudra, nor does he give a complete presentation of the instructions on dzogchen. Instead Khenpo Gangshar presents the most fundamental instructions of both mahamudra and dzogchen." - Thrangu Rinpoche, 'Vivid Awareness', 2011 p.19
Khenpo Gangshar's text on 'the resting meditation of the kusulu' also goes some way to explain where Chogyam Trungpa learnt the technique of training shamatha and vipashyana together.
"In general, meditation instructions often teach both tranquility and insight meditation. Many presentations teach that one should practice tranquility first and insight later. But here we meditate on the two together. We are taught to meditate on the nature of things by looking at them directly. If we can do this, our minds become peaceful. At the same time we will also develop the clarity of insight. In this way we do not seperate tranquility and insight; we pratcice them together." Vivid Awareness, p.116.
Khenpo Ganshar was famed to have very precise 'pointing out' instructions - but he believed that by developing insight and tranquility it makes it much more feasible to have a more stable realization of 'mahamudra/natural state/ordinary mind'. A direct paralell to Khenpo Gangshar's teaching of 'resting meditation' is in the inbreath component of the instruction. On the outbreath we are doing something, we are completely identifying with our body, our breathing, and we are 'following' it out into space, and dissolving - as the body breathes in, we are just resting. We aren't doing anything. This is very much the 'resting' style that Chogyam Trungpa was taught by Khenpo Gangshar as part of his 'mind instructions'.
"If you rest like that, your mind-essence is clear and expansive, vivid and naked, without any concerns of recollection or joy or pain. That is awareness. That is rigpa." Khenpo Gangshar, 'naturally liberating whatever you meet' (translated in accordance with the oral teaching of tulku urgyen rinpoche)
The other aspect of Khenpo Gangshar's mind instructions that can be seen mirrored in the instruction of Chogyam Trungpa is the 'distinguishing' ie: distinguishing between mind and awareness. When doing 'resting' meditation, (often referred to as rigpa/completion stage meditation), it can be common that pople think 'right, I'll just rest amd do nothing in this open space' and meanwhile they're comletely stuck in thought. Khenpo Gangshar emphasised the importance of distinguishing between sem and rigpa, or mind and awareness.
In Chogyam Trungpa's Instruction we see how the use of labelling/'secret mantra' lets us make this distinction, ie: when we are realise we are thinking we label it 'thinking' and go back to the breath. Now clearly, labelling is in no way unique. But the mahamudra view of thoughts is that the content is irrelevant, they are like 'fish jumping out of a great ocean'. When we have trained in this way it becomes a lot easier to let thoughts flow without getting hooked by them. It is encouraged that overtime we can just let thoughts arise and pass wihtout labelling, labelling is however, a very useful tool if we are completely scattered.
Ultimately, from the view of mahamudra, Chogyam Trungpa wanted people to be able to see that thoughts are appearances of the mind, and that they didn't threaten the 'natural state';
"People often try to discriminate between "good" thoughts and "bad" thoughts, like trying to separate milk from water. It is easy enough to accept the negative experiences in life but much harder to see the positive experiences as part of the path. Some individuals will be able to use both thoughts and the absence of thoughts as meditation, but it should be borne in mind that that which notes what is happening is the tight grip of ego.
It is likewise a mistake, when discursive thoughts are pacified, to overlook the clarity and regard the mind as merely blank. The experience of true insight is the simultaneous awareness of both stillness and active thoughts.
According to the maha ati teaching, meditation consists of seeing whatever arises in the mind and simply remaining in the state of nowness. Continuing in this state after meditation is known as "the post-meditation experience.
When we speak of "clarity" we are referring to that state which is free from sloth and dullness. This clarity, inseparable from pure energy, shines forth unobstructed. It is a mistake to equate clarity with awareness of thoughts and the colors and shapes of external phenomena.
When thoughts are absent the meditator is completely immersed in the space of non-thought. The "absence of thoughts" does not mean unconsciousness or sleep or withdrawal from the senses, but simply being unmoved by conflict. The three signs of meditation clarity, joy and absence of thoughts may occur naturally when a person meditates, but if an effort is made to create them the meditator still remains in the circle of samsara." - 'A teaching on the awakened state', commentary by Chogyam Trungpa Rinpoche
So there are a few factors there that have paralells in both mahamudra and dzogchen/maha-ati texts. In a vajrayana seminary text Chogyam Trungpa pretty much spells it out;
"So this teaches us to realise the indivisibilty of space and wisdom. The meditation practcie at this level is just mixing space and wisdom. This is very similar to the type of meditation that I have been teaching (publicly); the practice of dissolving yourself into space, or mixing the mind with space.' (CTR,'Tantric Path of Indestructible Wakefulness' p.688)
"In the kagyu (mahamudra) tradition, we employ a special practice technique, which is the experiencing of 'chung ne dro sum'....which is 'where thoughts arise, dwell and go;. Those three are accompanied by the practice of 'ying rik sewa', means 'mixing the concious mind with space'. Sometimes it is called 'lung sem sewa', mixing the mind amd breating.
In either case, the idea is to experience space." - CTR, 'The Path of Individual Liberation', p.281
Chogyam Trungpa wanted people to be able to glimpse this space and to be able to let go into that awareness. This is very much evident in the formless medtation instruction of Rigdzin Shikpo, which is essentially the eact same set of instructions (which he received in Oxford befroe Trungpa left fro America. He was trained in dzogchen from day one. Trungpa thought formless practice suited the English temperament heh) :
"It is what Trungpa Rinpoche called 'self-secret'. There is no problem is explaining the full technique to you becaseu what you get from it depends entirely on you. The meditation described here is commonly referred to as 'formless meditation'. We can call this a beginners pratcice in the sense that we start with it. In fact this a practice we never abandon. When we reach a higher level of experience we might have a high flown name like 'The Great Perfection'....we will find ourselves doing the same meditation.
Formless meditation is associated with the openness, clarity and sensitivity aspects of mind. Within this openness-clarity, gaps occur thatr make it very difficult to remain ego-centred. In the 'speech' aspect of this meditation we can begin by using the breath as a vehicle. As you breathe out, rest in the feeling of the breath leaving the body. Just allow the breath to go out naturally, with a sense of spaciousness and giving away, a sense of the breath giving way into space. Other than this, there is no need to concentrate on the breath in any particular way. You are not so much meditating on that breath than with the breath.
Let go into this sensation of space created by the outbreath. Don't think that you are filling up space like a giant balloon. Simply surrender to the feeling ouf spaciousness.
On the inbreath you can relax by not doing anything at all. As Trunga Rinpoche used to say "it's delightful to know that you don't have to do anything!". Just rest where you are.
Meditation is not like star trek: You are not using the spaceship of breath to voyange into infinite space. YOu are just relating to the space in an even greater way. YOu are not pushing out some 'space boundary'. With no boundaries to push back, it's enough to just rest in openness." - Rigdzin Shikpo, Never Turn Away, 2007, p.19,24,25.
"The out-breath moves into space and you just surrender to the feeling and you let yourself relax physically and mentally into that. If the mind rests naturally like this, then just let go more, you can use the outbreath again if that helps. If it does not help just continue to relate to space as in a natural way as possible. If you feel you need more help or get lost in thought, you can just return to the outbreath and repeat the instruction of letting go into space until a natural sense of space and awareness starts to develop." - Rigdzin Shikpo, 'Openness Clarity Sensitivity', 2000, p.36
So this notion of letting go into the empty, spacious 'nature of mind' is repeated again and again and really has it's foundations in the mahamudra lineage of the kagyu school from which Trungpa was trained.
"Traditionally, just being there is the outcome of the breathing teachnique. In the TIbetan Buddhist tradition of formless meditatiopn, you can drop the breath, you meditate without the focus on the breathing. The shikantaza pracitice of 'just sitting', from the Japanese Zen tradition, is similar. Some people find it easy to do formless meditation without any focus on the breath. For long-term sitting it would be advisable to start with the mindfulness of the breathing. Later, the awareness of breathing falls away and at that point you can just go along without it. That seems to be the most systematic approach." CTR, Prfound Tresury of The Ocean of Dharma, chapter on 'Mixing Mind with Space', p.283.
That's enough for now. Hope this is helpful and/or interesting.
The teacher will then give the next instruction, saying, “Now, don’t just notice whether there is stillness or thought occurrence. When there is thinking, look into the thinker. When there is stillness, look into what feels the stillness.”
The disciple will return entirely bewildered and say, “When I look into what feels the stillness, I don’t find anything whatsoever. When the thinking occurs and I look into what thinks, I don’t find any ‘thing’ either. Not only that, but both the thinking and the feeling of stillness disappear. Now what am I supposed to do? Before, I could take charge of something. I could identify the thinking and the stillness. But it’s not like that anymore. When I look into what thinks, the thinker vanishes. When I look into what is still, that’s also gone. I’m at a complete loss. I have lost both the thinker and that which feels still.”
The teacher will reply, “No, you are not at all at a complete loss. Now you have arrived at Mahamudra, at the nature of mind. You need to train in this for months and years. Before, you were only concerned with the manifestation, not with the nature. Now the manifestation has vanished. What is left is the nature itself.” That is the traditional way of pointing out Mahamudra.
Training in this fashion, there is no difference whatsoever between Mahamudra and Dzogchen practice. That is why so many great masters of the past have praised the Mahamudra system so highly. It is perfect for both a beginner of little capacity and for a person of great capacity. In Mahamudra there are no errors or sidetracks whatsoever.