Śatapatha Brāhmaṇa ("of a hundred paths") 8.7.2.13

8.7.2.13

ātmānamagre saṃcādayati | ātmā hyevāgre sambhavataḥ sambhavatyatha dakṣiṇam pakṣamatha pucamathottaraṃ taddakṣiṇāvṛttaddhi devatrātho evaṃ vā asāvāditya imāṃlokāndakṣiṇāvṛdanuparyaiti

The body (of the altar) he fills up first, for of (a bird) that is produced, the body is produced first, then the right wing, then the tail, then the left (wing): that is in the rightward (sunwise) way, for this is (the way) with the gods, and thus, indeed, yonder sun moves along these worlds from left to right.