Śatapatha Brāhmaṇa ("of a hundred paths") 14.3.1.1

14.3.1.1

sa vai tṛtīye'han ṣaṣṭhe vā dvādaśe vā pravargyopasadau samasya pravargyamutsādayatyutsannamiva hīdaṃ śirastadyadetamabhito bhavati tatsarvaṃ samādāyāgreṇa śālāmantarvedyupasamāyanti

Now, on the third, or the sixth, or the twelfth day, having combined (the two performances of) the Pravargya and Upasads, he 'sets out ' the Pravargya, for set out (removed), as it were, is this head (from the trunk). Having gathered together all around it (the Mahâvîra pot), they meet together upon the Vedi in the Sâlâ, (entering) by the front door.