Śatapatha Brāhmaṇa ("of a hundred paths") 3.4.1.22

3.4.1.22

athādharāraṇiṃ nidadhāti | urvaśyasītyathottarāraṇyājyavilāpanīmupaspṛśatyāyurasīti tāmabhinidadhāti purūravā asītyurvaśī vā apsarāḥ purūravāḥ patiratha yattasmānmithunādajāyata tadāyurevamevaiṣa etasmanmithunādyajñaṃ janayatyathāhāgnaye mathyamānāyānubrūhīti

Thereon he lays the lower churning-stick (with the top to the north), with, 'Thou art Urvasî!' He then touches the (ghee in the) ghee-pan with the upper churning-stick, with, 'Thou art Âyu,' he puts it down (on the lower arani) with, 'Thou art Purûravas.' For Urvasî was a nymph, and Purûravas was her husband; and the (child) which sprung from that union was Âyu: in like manner does he now produce the sacrifice from that union. Thereupon he says (to the Hotri), 'Recite to Agni, as he is churned!'