Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.5.20

4.2.5.20

gāyatrī vai prātaḥsavanaṃ vahati | triṣṭummādhyandinaṃ savanaṃ jagatī tṛtīyasavanaṃ tadvā anekākinyeva triṣṭummādhyandinaṃ savanaṃ vahati gāyatryā ca bṛhatyā cānekākinī jagatī tṛtīyasavanaṃ gāyatryoṣṇihakakubbhyāmanuṣṭubhā

The Gâyatrî, forsooth, bears the morning libation (to the gods), the Trishtubh the midday libation, and the Gagatî the evening libation,--but, then, the Trishtubh bears the midday libation, not alone, (but) with both the Gâyatrî and the Brihatî; and the Gagatî (bears) the evening libation, not alone, (but) with the Gâyatrî, the Kakubh, and Ushnih, and the Anushtubh.