2.1.19 When a man is in deep dreamless sleep… and is not aware of anything at all, this is what happens. There are 72,000 veins named hitā that run from the heart to the pericardium [the heart’s outer membrane]. He slips out of the heart through these veins and rests within the pericardium. He rests there oblivious to everything just as a young man, a great king or an eminent brahmin remain oblivious to everything at the height of sexual bliss.
3.4.2 Ushasta Cākrāyana retorted: “That’s a fine explanation!... Come on, give me a real explanation of Brahman which is plain and not cryptic, of the Self that is within all.”
“The Self within all is your Self within you”
“Which one is the Self within all, Yājnavalkya?”
“You cannot see the seer who does the seeing; you cannot hear the hearer who does the hearing; you cannot think of the thinker who does the thinking; and you cannot perceive the perceiver who does the perceiving. The Self within all is your Self within You. All else besides this is grief!”
Thereupon, Ushasta Cākrāyana fell silent.
4.3.20 Now, he has these veins called hitā. They are fine as a hair split a thousandfold and filled with white, blue, orange, green and red fluid….
4.3.30 Nor does he perceive anything here, but although he does not perceive, he is quite capable of perceiving, for it is impossible for the perceiver to lose his capacity to perceive, for it is indestructible. But there isn’t a second reality here that he could perceive as something distinct and separate from himself.
31 When there is some other thing, then the one can see the other, the one can smell the other, the one can taste the other, the one can speak to the other, the one can hear the other, the one can think of the other, the one can touch the other, the one can perceive the other.
32 He becomes the one ocean, he becomes the sole seer! This,Your Majesty, is the world of Brahman.”
8.6 Now, these veins of the heart consist of the finest essence of orange, white, blue, yellow and red. The Sun up there, likewise, is orange, white, blue, yellow and red. Just as a long highway traverses both the villages, near and far, so also these rays of the Sun traverse both worlds, the one down here and the one up above. Extending out from the Sun up there, they slip into these veins here, and extending out from these veins here, they slip into the Sun up there.
So, when someone is sound asleep here, totally collected and serene, and sees no dreams, he has then slipped into these veins. No evil thing can touch him, for he is then linked with Radiance.
Now, when someone here has become extremely infirm, people sit around him and ask: “Do you recognize me?” As long as he has not departed the body, he would recognize them. But when he is departing from the body, he rises up along those same rays. He goes up with the sound OM.
101, the veins of the heartOne of them runs up to the crown of the head.Going up by it, he reaches the immortal.The rest, in their ascent, spread out in all directions.
Excerpts from Upanishads adapted from Oxford World's Classics edition translated by Patrick Olivelle. Image of heart/pericardium taken from yin-informationtechnology.blogspot.com; image of King Janaka of Videha taken from Krishnasmercy.org; photo of stained glass window from Nieuwe Kerk, Delft, Netherlands taken by Meeg on May 28, 2008.