Shatapatha Brahmana 8.3.4.15

8.3.4.15

atha yāḥ sapta paścāt | ya eveme sapta paścātprāṇāstānasminnetaddadhāti tā anantarhitā etābhyo dvādaśabhya upadadhātyanantarhitāṃstadātmanaḥ prāṇāndadhāti sa eṣa vāyuḥ prajāpatirasmiṃstraiṣṭubhe 'ntarikṣe samantam paryaknastadyattṛtīyāṃ citimupadadhāti vāyuṃ caiva tadantarikṣaṃ ca saṃkkṛtyopadhatte 'tha lokampṛṇe upadadhātyasyāṃ sraktyāṃ tayorupari bandhuḥ purīṣaṃ nivapati tasyopari bandhuḥ

And the seven he places at the back (of the altar) are those seven vital airs behind: it is these he thereby puts into him. He places them so as not to be separated from those twelve (Khandasyâs): he thereby puts into him vital airs that are not separate from the body. That same Vâyu-Pragâpati is turned round in all directions in this trishtubh-like air; and when he lays down the third layer, having made up both Vâyu (the wind) and the air, he thereby adds them to himself. He then puts down two Lokamprinâ (space-filling bricks) in that corner: the significance of them (will be explained) further on. He throws loose earth (on the layer): the significance of this (will be explained) further on.