Shatapatha Brahmana 4.5.5.12

4.5.5.12

pañca ha tveva tāni pātrāṇi | yānīmāḥ prajā anu prajāyante samānamupāṃśvantaryāmayoḥ śukrapātramṛtupātramāgrayaṇapātramukthyapātram pañca vā ṛtavaḥ saṃvatsarasya saṃvatsaraḥ prajāpatiḥ prajāpatiryajño yadyu ṣaḍevartavaḥ saṃvatsarasyetyādityapātramevaiteṣāṃ ṣaṣṭham

Now, these same cups after which creatures are produced, are five,--those of the Upâmsu and Antaryâma (counting as) one and the same, the Sukra cup, the Ritu cup, the Âgrayana cup, and the Ukthya cup; for there are five seasons in the year, and Pragâpati is the year, and the sacrifice is Pragâpati. But if there be six seasons in the year, then the Âditya cup is the sixth of them.