Varahashrautasutra 3.2.2.39

3.2.2.39

samūḍhaṃ cedaindravāyavāgrau prāyaṇīyodayanīyau daśamaṃ cāhaḥ | itareṣāṃ navānāmaindravāyavāgraṃ prathamamahaḥ | atha śukrāgramathāgrāyaṇāgramiti trirabhyasya

If it is unshifted: the introductory day, the concluding day, and the tenth day have the Aindravāyava cup first; among the other nine [days], the first day has the Aindravāyava cup first, then having the Śukra cup first, then having the Āgrāyaṇa cup first—repeating this three times.