Śatapatha Brāhmaṇa ("of a hundred paths") 13.8.3.9

13.8.3.9

tāsāmekām madhye prācīmupadadhāti sa ātmā tisraḥ purastānmūrdhasa+hitāstacirastisro dakṣiṇataḥ sa dakṣiṇaḥ pakṣastisra uttarataḥ sa uttaraḥ pakṣastisraḥ paścāttatpucaṃ so'syaiṣa pakṣapucavānātmā yathaivāgnestathā

One of them he places in the middle, with the front side towards the east: this is the body (trunk);--three in front, fitted to (the position of) the head: that is the head;--three on the right; that is the right wing (side);--three on the left: that is the left wing;--three behind: that is the tail. Thus this his body, furnished with wings and tail, is just like that of Agni (the fire-altar).