Śatapatha Brāhmaṇa ("of a hundred paths") 8.1.4.1

8.1.4.1

tā haike puruṣamupārpyopadadhati | eṣa vai prāṇastametā bibhrati yatprāṇam bibhrati tasmātprāṇabhṛta iti na tathā kuryādeṣo 'haiva prāṇo ya eṣa hiraṇmayaḥ puruṣastasya tvayamātmā yāvadidamabhyayamagnirvihitastadyaddhāsyaitā aṅga nābhiprāpnuyuḥ prāṇo hāsya tadaṅgaṃ nābhiprāpnuyādyadu vai prāṇo 'ṅgaṃ nābhiprāpnoti śuṣyati vā vai tanmlāyati vā tasmādenāḥ pariśritsvevopārpyopadadhyādatha yā madhya upadadhāti tābhirasyaiṣa ātmā pūrṇastā u evaitasmādanantarhitāḥ

Now some lay down (these bricks) so as to be in contact with the (gold) man, for he is the vital air, and him these (bricks) sustain; and because they sustain (bhri) the vital air (prâna), therefore they are called 'Prânabhritah.' Let him not do so: the vital air is indeed the same as that gold man, but this body of his extends to as far here as this fire (altar) has been marked out. Hence to whatever limb of his these (breath-holders) were not to reach, that limb of his the vital air would not reach; and, to be sure, to whatever limb the vital air does not reach, that either dries up or withers away: let him therefore lay down these (bricks) so as to be in contact with the enclosing stones; and by those which he lays down in the middle this body of his is filled up, and they at least are not separated from him.