Kauṣītaki (Śāṅkhāyana) Brāhmaṇa 19.1.6

19.1.6

agnaye kṣatra bhūte dvādaśa kapālam /

xix. 1. They being about to consecrate themselves gather together the fires; verily thus they place might and strength in one place in themselves. Then they perform the gathering together sacrifice; they offer a cake on eight potsherds to Agni of the holy power, to Agni of the lordly power one on eleven potsherds, to Agni, supporter of the lordly power, one on twelve potsherds. Verily thus the sacrificers mount on the holy power and the lordly power; verily thus with them in safety they pass over the year. Of many who are about to pile (the fire) this is the gathering together (offering), connected with the bringing together of the firepan; for one who is about to consecrate himself it is the same.