I haven't done a lot of kasina work using a candle as the object, but I've done a decent amount of staring at a moving ceiling fan instead. I can speak a bit about what head tension is like in my practice.
While visual kasina practice definitely highlights impermanence due to the rapidly fluctuating images in the visual field, there's an even more interesting no-self aspect to it that highlights the lack of a fixed self doing the looking. It's also related a bit to the skewed spatial structure of the visual field, how that is related to the experience of specific muscle tensions all around the head, and how that's all misread to reinforce the illusion that "you" are "looking" at things. I'm also going to write this from the pre-stream entry point of view, so your attainments or perceptual shifts may change your experience of this, and there may well be important differences from my experience keeping my eyes open most of the time versus closing them to focus on the nimitta that develops.
For me, the visual field seems like an infinite cone with a few special areas. One is the point of visual focus somewhere in the volume of the cone, which what you're looking at. Another is a centerpoint, where "you" are looking from. The centerpoint can be felt back behind the two eyes somewhere in the middle of the head near the pineal gland, and is the same as the third eye chakra. I'm not sure if it's muscle tension or a feature of the visual field, but there's a strong feeling of movement and directionality flowing from behind through the centerpoint and pushing attention back out to somewhere in the volume of the cone. I'm told that sixth jhana feels the same way, but haven't been there myself. Focusing on the the feeling of flow through the centerpoint is one method of getting into the Witness and progressing up through the jhanas/nanas. The centerpoint itself can seem incredibly hard to focus on or rest at -- it's almost like a discontinuity that you can't quite rest at or look at, and it feels increasingly aversive the closer you get.
The cone itself can look around in any direction from the centerpoint, and can seem to be anchored down to the rest of the body by the central channel, a stiff rod that goes down through the throat/spinal cord. This feels a little bit like an architect's lamp which swivels around and looks in all directions. The edges of the "cone" are really indistinct and hard to define exact boundaries, but sometimes third jhana for me feels like I am the edges of the cone swiveling around but not anything on the interior volume of the cone. If you mess around with vipassanizing this stuff enough, you can also get the felt feeling of the cone to swivel around independently of the movement of your head or the contents of the visual field, which is a great way to make yourself dizzy.
The basic perceptual geometry of the visual field in terms of focus point/edges/centerpoint doesn't change based on the direction you're looking, but strangely enough the direction of flow can change such that you're looking behind "you" out the back of your head. When this happens, it can feel like everything you see in the visual field is "looking at" the centerpoint/"you" in through the back of your head, where "looking at" is a felt feeling that arises in awareness. This can also lead to a different variation on the Witness.
Muscle tension and other bodily sensations can easily be co-opted into feeling like the same thing as the centerpoint or the edges of the cone. I think the pre-meditation default for most people is that there's a little dot of muscle tension at their centerpoint, and that is where they "look" from and are. Interestingly, the centerpoint can shift location backwards when you close your eyes compared to when they're open. There can also be rhythmic pulses right at/around the centerpoint, and it sometimes feels like there's a little gyroscope turning right at the centerpoint. If you pay exclusive attention to these pulses, sometimes it feels like you get sucked into the exact centerpoint while everything squishes in/out around you. Muscle tension all around the head and eyes can be felt to be the edges of the cone.
There's a recurrring pattern in normal perception where attention alternates rapidly from the focus point out in the volume of the visual field back to the muscle tension at the centerpoint. From there, it can flash to a internal verbal thought or emotion judging what it's seeing, or directly back out into the visual field. I don't have Daniel's knack for timing stuff by Hz, but it seems like this loop happens several times a second. It also seems like it's connected to the basic perceptual duality of going out and getting something and bringing it back to "you". There's a good discussion of this in the
Empty Hands thread as the "attention tendril", and may be the same as the "attention wave" in Daniel's
Experiments in Actualism. Directly perceiving this attention wave going on and that you're actually failing to "bring back the bacon" from the focus point to the centerpoint generates a lot of suffering and aversion to looking at the process any more closely. That's because seeing the impermance and no-self in the attention loop directly implies seeing the suffering in the loop.
I'm not sure that there's a good way to make progress with visual kasina stuff without ever having some aversion or muscle strain appear. For me, I really need to just accept that aversion is arising, treat it as a sensation, and keep on going anyways in order to make it out through Reobservation to Equanimity when doing kasina work. It could also be that you're looking fairly closely at this stuff and starting to notice that the muscle tension at the centerpoint isn't the same thing as the other stuff in the visual field. Your mind then might subconsciously intensify the muscle tension at the centerpoint to make it easier to find, which then has the paradoxical positive feedback of making it both more painful and more obvious that it's not "you".
Here's a few things that can occasionally affect it and that may be worth trying out to see what effect they have:
- There's a perceptual state you can get into where you start to perceive the boundaries of the body in terms of the felt appearance of the body parts rather than what you know they look like in the visual field. Usually the head and hands feel suddenly huge, like a
cortical homunculus. This is also related to what Culadasa calls the "acquired appearance of the breath", where you start perceiving the breath sensations more clearly in a different perceptual context. You could try to keep this feeling in awareness while focusing on the flame. Touching the area with your hand may be triggering a move more towards this method of perceiving the interior of the head as unrelated to the visual field.
- Blink your eyes, feeling the change in location of the centerpoint with the eyes closed versus open.
- Flicker your eyes rapidly while keeping focus on the centerpoint, which can very rapidly carry you up through the nanas towards your current cutting-edge. I think that's because the rapid all-or-nothing changes feel very similar to the strobing formations in High Equanimity. This is also the classic cessation test to determine whether you've achieved stream entry. I'm not sure whether I'm working on first or second path, but just blinking my eyes rapidly has been a really useful tool for getting up into Equanimity quickly when practicing. A minute or two of it can be the equivalent of spending 10-30 minutes on preliminary kasina work.
- If you've got prior experience in resting in/as awareness, that may reduce the aversion and tension.
- Resting in the Witness/sixth jhana feeling if you've experienced that before may help. Sometimes putting attention on the centerpoint and the flow feels like it blocks out the feeling of their being a separate self and makes it easier to rest in something more like just awareness.
- On the flip side, observe the loop closely and try to get used to how the focus point/centerpoint/edges/central channel feel in your experience. You can also try to look out the back of your head and to look right at the centerpoint by placing the focus point at the centerpoint. All of these are also good ways to develop a feel for the Witness if you're interested in going up the jhanic arc with it.
- If you get them, dive into following the rhythmic pulses at the centerpoint.
- Close your eyes, and feel like your eyes are turning around and looking first up in the crown of your head and then to the back. Then have them try to look directly back at the centerpoint. This will be aversive, and even more so the closer you are to looking at the centerpoint. If you keep going anyway, you'll rise up through the jhanas/nanas and eventually all the resistance will melt away up in Equanimity. You'll then drop down to pushing on your throat chakra and so forth until your subtle body disappears or becomes very malleable-feeling. This can feel like you're confused who the experience is actually happening to. This method is unpleasant and could very well cause eye strain -- it might be better to use other practices to gently loosen up the energy body or get into Equanimity another way before beginning kasina practice.
I've got no idea on what the commentaries say about the mantra, but I think it could be useful because of the possible sidetrip to thoughts in the core attention loop. If you're trying to unravel what it feels like to be both the "I" in "I think" and "I" in "I am currently seeing", then doing a mantra means that when attention shifts to thoughts from the tension at the centerpoint, it hits a mantra that you're keeping track of and you get to see that part of the loop too. This may be more useful if you're doing it as mixed samatha-vipassanna practice where you're deliberately allowing alternating attention -- maybe pure concentration practice you'd be better off just learning to keep attention thoroughly focused on just individual visual sensations. I just use "Om mani padme hum", and try to pay attention to how it interleaves with both the sensations at the focus point and the centerpoint and it changes through time along with the visual changes.
This is all based on my personal experience with the ceiling fan kasina, as well as advice from Shargrol and a number of other threads both here and from KFD. I'd be interested in hearing if it differs for those using the candle flame, and would love to hear other's experiences with blinking rapidly or watching a moving ceiling fan. I think there also are probably some other interesting correspondences between the jhanas and different portions of the visual field being watched or felt to be self, and would love to hear more from others with experience in both. I know kasina practice is mainly billed as helping with concentration, but it seems like it and other work with the visual field can put you in contact with some of the core perceptual issues that insight practice is trying to resolve.
