Shatapatha Brahmana 13.5.1.1

13.5.1.1

atha prātargotamasya caturuttara stomo bhavati tasya catasṛṣu bahiṣpavamānamaṣṭāsvaṣṭāsvājyāni dvādaśasu mādhyandinaḥ pavamānaḥ ṣoḍaśasu pṛṣṭhāni viṃśatyāmārbhavaḥ pavamānaścaturviṃśatyāmagniṣṭomasāma

Then, on the morrow, there is (used) Gotama's Stoma (form of chanting) successively increasing by four (verses): the Bahishpavamâna thereof is on four, the Âgya (stotras) on eight, the Mâdhyandina Pavamâna on twelve, the Prishtha (stotras) on sixteen, the Ârbhava Pavamâna on twenty, and the Agnishtoma-sâman on twenty-four (verses).