Shatapatha Brahmana 10.5.5.7

10.5.5.7

sa yatprāñcam puruṣamupadadhāti prācyau srucau tatprāṅ cīyate'tha yatpratyañcaṃ kūrmamupadadhāti pratyañci paśuśīrṣāṇi tatpratyaṅ cīyate'tha yannyañcaṃ kūrmamupadadhāti nyañci paśuśīrṣāṇi nīcīriṣṭakāstannyaṅ cīyate'tha yaduttānam puruṣamupadadhātyuttāne srucā uttānamulūkhalamuttānāmukhāṃ taduttānaścīyate'tha yatsarvā anu diśaḥ parisarpamiṣṭakā upadadhāti tatsarvataścīyate

When he lays down the (gold) man with his head forward (eastward), and the two spoons (with their bowls) forward, thereby he (Agni) is built looking forward; and when he lays down the tortoise with its head backward (westward), and the victims’ heads turned backward, thereby he is built looking backward; and when he, lays down the tortoise with its face downward, and the victims’ heads with their faces downward, and the bricks with their faces downward, thereby he is built looking downward; and when he lays down the (gold) man with his face upward, and the two spoons (with their open bowls) turned upward, and the mortar turned upward, and the fire-pan turned upward, thereby he is built looking upward; and when he lays down the bricks whilst moving round (the altar) in every direction, thereby he is built (looking) in all directions.