Śatapatha Brāhmaṇa ("of a hundred paths") 8.1.4.10

8.1.4.10

atha ha smāha svarhinnāgnajitaḥ | nagnajidvā gāndhāraḥ prāṇo vai samañcanaprasāraṇaṃ yasminvā aṅge prāṇo bhavati tatsaṃ cāñcati pra ca sārayati saṃcitamevainam bahiṣṭādabhyanyāttadasminprāṇaṃ samañcanaprasāraṇaṃ dadhāti tathā saṃ cāñcati pra ca sārayatīti tadahaiva samañcanaprasāraṇaṃ yatsa taduvāca rājanyabandhuriva tveva taduvāca yannu śataṃ kṛtvo 'tho sahasram bahiṣṭādabhyanyurna vai tasmiṃste prāṇaṃ dadhyuryo vā ātmanprāṇaḥ sa eva prāṇastadyatprāṇabhṛta upadadhāti tadasminprāṇaṃ samañcanaprasāraṇaṃ dadhāti tathā saṃ cāñcati pra ca sārayatyatha lokampṛṇe upadadhātyasyāṃ sraktyāṃ tayorupari bandhuḥ purīṣaṃ nivapati tasyopari bandhuḥ

And Svargit Nâgnagita or Nagnagit, the Gândhâra, once said, 'Contraction and expansion surely are the breath, for in whatever part of the body there is breath that it both contracts and expands; let him breathe upon it from outside when completely built: he thereby lays breath, the (power of) contraction and expansion, into it, and so it contracts and expands.' But indeed what he there said as to that contraction and expansion, it was only one of the princely order who said it; and assuredly were they to breathe upon it from outside a hundred times, or a thousand times, they could not lay breath into it. Whatever breath there is in the (main) body that alone is the breath: hence when he lays down the Prânabhritah (breath-holders), he thereby lays breath, the (power of) contraction and expansion, into it; and so it contracts and expands. He then lays down two Lokamprinâ (bricks) in that corner: the meaning of them (will be explained) further on. He throws loose earth (on the layer): the meaning of this (will be explained) further on.