I was going to answer "Your practice journal" - but that's not 1000y old.
I don't know... old texts can be really inaccessible. How does selecting for obscurity prevent a selection bias? To understand the really old texts, you'd need lots of explanatory material...
Why are you asking? Convoluted way of getting reading recommendations? Ideas for your next novel? Hmmm... steam-punk post zombie-apocalyptic retro-dharma...

Or are you trying to re-create the Orance Catholic Bible?
Mix traditions. Some Pre-Socratics, Epicurus, Sappho, some bits of Plato's Socratic dialogues, a few technical suttas (Anapanasati Sutta, Bahiya Sutta, Satipatthana Sutta, Dhammapada, Fruits of the contemplative life, Songs of the Nuns/Therigatha ... you get the picture), St. Augustine's refutations of the Manicheans, the Tao Te Ching, the story of Rabia Basri, the Gospel of Thomas, the Gospel of Mark... Oh, and the verse form of the "Perfection of Wisdom" Sutra, what's it called: the Ratnaguna (to save space, since the PoW is so long).
What would you put in there?
Cheers,
Florian