Śatapatha Brāhmaṇa ("of a hundred paths") 7.4.2.2

7.4.2.2

yadveva svayamātṛṇāmupadadhāti | prāṇo vai svayamātṛṇā prāṇo hyevaitatsvayamātmana ātṛntte prāṇamevaitadupadadhāti tāmanantarhitām puruṣādupadadhāti prāṇo vai svayamātṛṇeyaṃ vai svayamātṛṇeyamu vai prāṇo yaddhi kiṃ ca prāṇīyaṃ tatsarvam bibhartyanantarhitamevāsmādetatprāṇaṃ dadhātyuttarāmuttaramevāsmādetatprāṇaṃ dadhāti

And, again, why he puts on a naturally-perforated one;--the naturally-perforated (brick) is the breath (or vital air), for the breath thus bores itself (svayam âtrintte) through the body: it is breath he thus bestows on it. He puts it so as not to be separate from the man; for the naturally-perforated one is the breath, and the naturally-perforated one is this earth, and this earth is the breath, since this earth bears everything that breathes: he thus puts the breath so as not to be separate from him. Upon (the man he places the brick): he thus puts the breath upon him.