Śatapatha Brāhmaṇa ("of a hundred paths") 8.7.3.2

8.7.3.2

sa vai svayamātṛṇāyāmāvapati | prāṇo vai svayamātṛṇānnam purīṣam prāṇe tadannaṃ dadhāti tena sarvamātmānam pracādayati tammādyatprāṇe 'nnaṃ dhīyate sarvamātmānamavati sarvamātmānamanuvyeti

He also strews it on (the place where lies) the naturally-perforated (brick), for the naturally-perforated one means vital air, and the loose soil means food: he thus puts food into (the channels of) the vital air. In that manner he covers the whole body (of the altar); whence the food which is put into (the channels of) the vital air benefits the whole body, extends over the whole body.