Shatapatha Brahmana 10.1.2.9

10.1.2.9

atha hotā sapta candāṃsi śaṃsati caturuttarāṇyekarcāni virāḍaṣṭamāni teṣāṃ tisraścāśītayo'kṣarāṇi pañcacatvāriṃśacca tato yā aśītayaḥ saivāśītīnāmāptiraśītibhirhi mahadukthamākhyāyate'tha yāni pañcacatvāriṃśattato yāni pañcaviṃśatiḥ sa pañcaviṃśa ātmā yatra vā ātmā tadeva śirastatpakṣapucānyatha yāni viṃśatistadāvapanametāvadvai mahadukthaṃ tadetadatraiva mahadukthamāpnoti tāni vā etāni sarvāṇi jyotiṣṭoma evāgniṣṭoma āpyante tasmādu jyotiṣṭomenaivāgniṣṭomena yajeta

And the Hotri recites seven metres--each subsequent one-versed (metre) increasing by four (syllables)--with the Virâg as an eighth: these (eight) consist of three eighties and forty-five syllables. Now by the eighties thereof the eighties (of the mahad uktham) are obtained, for the Great Litany is counted (or recited) by eighties (of triplets); and of the forty-five (syllables which remain) twenty-five are this twenty-five-fold body; and where the body is there, indeed, are (included) the head, and the wings and tail; and the twenty (syllables which remain) are the insertion;--thus much, then, is the Great Litany: thereby he obtains the Great Litany even in this (Agnishtoma). All these (three) are indeed obtained in the Gyotishtoma Agnishtoma: let him, therefore, perform offering with the Gyotishtoma Agnishtoma.