Varahashrautasutra 3.2.2.40

3.2.2.40

vyūḍhasyaindravāyavāgrau prāyaṇīyodayanīyau | itareṣāṃ daśānāmaindravāyavāgraṃ prathamamahaḥ | atha dve āgrāyaṇāgre athaindravāyavāgramatha dve śukrāgre athāgrāyaṇamatha dve aindravāyavāgre

Of the shifted [sacrifice], the introductory and concluding [days] have the Aindravāyava cup first; among the other ten [days], the first day has the Aindravāyava cup first; then two days having the Āgrāyaṇa cup first, then having the Aindravāyava cup first, then two days having the Śukra cup first, then the Āgrāyaṇa cup first, then two days having the Aindravāyava cup first.