Shatapatha Brahmana 2.5.4.10

2.5.4.10

atha vaiśvakarmaṇa ekakapālaḥ puroḍāśo bhavati | viśvaṃ vā etatkarma kṛtaṃ sarvaṃ jitaṃ devānāmāsītsākamedhairījānānāṃ vijigyānānāṃ viśvamvevaitasyaitatkarma kṛtaṃ sarvaṃ jitam bhavati sākamedhairījānasya vijigyānasya tasmādvaiśvakarmaṇa ekakapālaḥ puroḍāśo bhavati

Then follows a cake on one potsherd for Visvakarman. To the gods, indeed, on performing the Sâkamedha-sacrifice and obtaining the victory (over Vritra), that sacred work (karman) was made complete (visva), and all was conquered; and so is that sacred work made complete, and all is conquered, by him who has performed the Sâkamedha-sacrifice and obtained the victory: hence there is a cake on one potsherd for Visvakarman.