Śatapatha Brāhmaṇa ("of a hundred paths") 5.2.3.6

5.2.3.6

atha śvo bhūte | āgnāvaiṣṇavamekādaśakapālam puroḍāśaṃ nirvapati tena yatheṣṭyaivaṃ yajate tadyadevādaḥ prajātamāgnāvaiṣṇavaṃ dīkṣaṇīyaṃ havistadevaitadagnirvai sarvā devatā agnau hi sarvābhyo devatābhyo juhvatyagnirvai yajñasyāvarārdhyo viṣṇuḥ parārdhyastatsarvāścaivaitaddevatāḥ parigṛhya sarvaṃ ca yajñam parigṛhya sūyā iti tasmādāgnāvaiṣṇava ekādaśakapālaḥ puroḍāśo bhavati tasya hiraṇyaṃ dakṣiṇāgneyo vā eṣa yajño bhavatyagne reto hiraṇyaṃ yo vai viṣṇuḥ sa yajño 'gniru vai yajña eva tadu tadāgneyameva tasmāddhiraṇyaṃ dakṣiṇā

And on the following day he prepares a cake on eleven potsherds for Agni and Vishnu, and offers it in the same way as the (regular) ishti: this indeed is just what that approved initiation-offering to Agni and Vishnu is there. Now Agni is all the deities, since in Agni one offers to all deities; and Agni forsooth is the lower end, and Vishnu is the upper end: 'May I be consecrated, after thus encompassing all the deities, and after encompassing the whole sacrifice!' thus he thinks, and hence there is a cake on eleven potsherds to Agni and Vishnu. Gold is the sacrificial fee for this (offering); for to Agni belongs this sacrifice, and gold is Agni's seed. As to Vishnu, he is the sacrifice, and Agni forsooth is the sacrifice: nevertheless this is Agni's alone, therefore gold is the fee.