Shatapatha Brahmana 5.5.4.33

5.5.4.33

sa yadi haitayāpi somātipūtam bhiṣajyet | iṣṭā anuyājā bhavantyavyūḍhe srucāvathaitairhavirbhiḥ pracarati paścādvai somo 'tipavate paścādevainametena medhenāpidadhātyāśvinamu tarhi dvikapālam puroḍāśaṃ nirvapedatha yadā vapābhiḥ pracaratyathaitenāśvinena dvikapālena puroḍāśena pracarati

And if by that (Sautrâmanî-offering) he would heal one purged by Soma, then--(after) the after-offering (of the animal sacrifice) has been performed, and the two spoons separated--he proceeds with those (three) oblations. For it is towards the back part that Soma flows through, and at the back part (of the sacrifice) he thus closes him up by that sacrificial essence. Let him in that case prepare a cake on two potsherds for the Asvins; and when he proceeds with the offering of the omenta, then he also proceeds with that two-kapâla cake for the Asvins.