Pitṛgaṇa-Vibhāga (Classification of the Pitṛs) and the Śrāddha–Soma Nourishment Cycle
एतेषामभ्युपगमान्मनुर्मन्वन्तरेश्वरः / मन्वन्तरादौ श्राद्धानि प्रवर्तयति सर्वशः
eteṣāmabhyupagamānmanurmanvantareśvaraḥ / manvantarādau śrāddhāni pravartayati sarvaśaḥ
Accepting these ordinances, Manu, the lord of the Manvantara, at the very beginning of the Manvantara sets the Śrāddha rites in motion everywhere.