The Upanishads, Part 1 (SBE01), by Max Müller, , at sacred-texts.com
1. Pragâpati said: 'The Self which is free from sin, free from old age, from death and grief, from hunger and thirst, which desires nothing but what it ought to desire, and imagines nothing but what it ought to imagine, that it is which we must search out, that it is which we must try to understand. He who has searched out that Self and understands it, obtains all worlds and all desires.'
2. The Devas (gods) and Asuras (demons) both heard these words, and said: 'Well, let us search for that Self by which, if one has searched it out, all worlds and all desires are obtained.'
Thus saying Indra went from the Devas, Virokana from the Asuras, and both, without having communicated with each other, approached Pragâpati,
holding fuel in their hands, as is the custom for pupils approaching their master.
3. They dwelt there as pupils for thirty-two years. Then Pragâpati asked them: 'For what purpose have you both dwelt here?'
They replied: 'A saying of yours is being repeated, viz. "the Self which is free from sin, free from old age, from death and grief, from hunger and thirst, which desires nothing but what it ought to desire, and imagines nothing but what it ought to imagine, that it is which we must search out, that it is which we must try to understand. He who has searched out that Self and understands it, obtains all worlds and all desires." Now we both have dwelt here because we wish for that Self.'
Pragâpati said to them: 'The person that is seen in the eye 1, that is the Self. This is what I have said. This is the immortal, the fearless, this is Brahman.'
They asked: 'Sir, he who is perceived in the water, and he who is perceived in a mirror, who is he?'
He replied: 'He himself indeed is seen in all these 2.'
134:1 Prasna Up. II, 1.
134:2 The same verse occurs in the Katha 6, 16, and is frequently quoted elsewhere, for instance, Mait. comm. p. 164. For vishvann, the right reading would seem to be vishvak. In the Mait. Up. VI, 30, the Trishtubh are reduced to Anushtubh verses. See also Prasna Up. III, 6-7; Mund. Up. II, 2.
134:3 Here the highest problem is treated again, the knowledge of the true Self, which leads beyond the world of Brahmâ (masc.), and enables the individual self to return into the Highest Self.
135:1 The commentator explains this rightly. Pragâpati means by the person that is seen in the eye, the real agent of seeing, who is seen by sages only, even with their eyes shut. His pupils, however, misunderstand him. They think of the person that is seen, not of the person that sees (Yoga-sûtras II, 6). The person seen in the eye is to them the small figure imaged in the eye, and they go on therefore to ask, whether the image in the water or in a mirror is not the Self.
135:2 The commentators are at great pains to explain that Pragâpati told no falsehood. He meant by purusha the personal element in the highest sense, and it was not his fault that his pupils took purusha for man or body.