Śatapatha Brāhmaṇa ("of a hundred paths") 9.4.1.2

9.4.1.2

yadvevaitā rāṣṭrabhṛto juhoti | prajāpatervisrastānmithunānyudakrāmangandharvāpsaraso bhūtvā tāni ratho bhūtvā paryagacattāni parigatyātmannadhattātmannakuruta tathaivainānyayametatparigatyātmandhatta ātmankurute

And, again, as to why he offers the Realm-sustaining (oblations). From Pragâpati, when dismembered, couples went forth, in the form of Gandharvas and Apsaras; and he, having turned into a chariot, enclosed them, and having enclosed them, he took them to himself and made them his own; and in like manner does this (Sacrificer), thereby enclosing them, take them to himself and make them his own.