The Upanishads, Part 2 (SBE15)
Chapters
Prasna-Upanishad: Sixth Prapathaka

'What is without thought, though placed in the centre of thought, what cannot be thought, the hidden, the highest--let a man merge his thought there: then will this living being (linga) be without attachment .'

20. And thus it has been said elsewhere: There is the superior fixed attention (dharana) for him, viz. if he presses the tip of the tongue down the palate and restrains voice, mind, and breath, he sees

Brahman by discrimination (tarka). And when, after the cessation of mind , he sees his own Self, smaller than small, and shining, as the Highest Self , then having seen his Self as the Self, he becomes Self-less, and because he is Self-less, he is without limit, without cause, absorbed in thought. This is the highest mystery, viz. final liberation. And thus it is said:

'Through the serenity of the thought he kills all actions, good or bad; his Self serene, abiding in the Self, obtains imperishable bliss.'

2 1. And thus it has been said elsewhere: The artery, called Sushumna, going upwards (from the heart to the Brahmarandhra), serving as the passage of the Prana, is divided within the palate. Through that artery, when it has been joined by the breath (held in subjection), by the sacred syllable Om, and by the mind (absorbed in the contemplation of Brahman), let him proceed upwards , and after turning the tip of the tongue to the palate, without using any of the organs of sense, let greatness perceive greatness . From thence he goes to selflessness, and through selflessness he ceases to be an enjoyer of pleasure and pain, he obtains aloneness (kevalatva, final deliverance). And thus it is said:

'Having successively fixed the breath, after it had been restrained, in the palate, thence having crossed the limit (the life), let him join himself afterwards to the limitless (Brahman) in the crown of the head.'

22. And thus it has been said elsewhere: Two Brahmans have to be meditated on, the word and the non-word. By the word alone is the non-word revealed. Now there is the word Om. Moving upward by it (where all words and all what is meant by them ceases), he arrives at absorption in the non-word (Brahman). This is the way, this is the immortal, this is union, and this is bliss. And as the spider, moving upward by the thread, gains free space, thus also he who meditates, moving upward by the syllable Om, gains independence.