Agniveshyagrihyasutra 3.6.4.2

3.6.4.2

atha yadyanuhṛtāḥ syuryasyakasyacidaśvatthasyāraṇī gṛhītvā mathitvāgnimupasamādhāya paristīrya kṛṣṇājine śamyāyāṃ dṛṣadupale yuktvāsthīnyevāñjanaṃ piṣṭvā purāṇena sarpiṣā samudāyutya juhvā prasekaṃ juhoti asmāttvamadhijāto 'smayaṃ tvadadhijāyatām \

Now, if they have been carried along, having taken churning sticks of any aśvattha tree whatsoever, having churned, having set up the fire, having strewn [darbha grass] around, having joined the upper and lower millstones upon the black antelope skin [and] upon the wooden peg, having ground the bones like collyrium, having stirred them with old clarified butter, he offers a continuous stream with the juhū ladle: “From this you were born; from you may this one be born!