Shatapatha Brahmana 4.5.9.2

4.5.9.2

atha caturthe 'hanvyūhati | grahānyūhanti candāṃsi tadāgrayaṇāgrān gṛhṇāti prājāpatyaṃ vā etaccaturthamaharbhavatyātmā vā āgrayaṇa ātmā vai prajāpatistasmādāgrayaṇāgrāngṛhṇāti

Then, on the fourth day, he transposes the grahas, and they transpose the metres. There he draws the cups beginning with the Âgrayana,--for that fourth day is Pragâpati's own; and the Âgrayana is the self, and Pragâpati is the self: therefore he draws the cups beginning with the Âgrayana.