Yuga-Vibhāga and Kāla-Pramāṇa
Measures of Time and the Four Yugas
तेषां तु तप्ततपसा आर्षेणोपक्रमेण तु / सप्तर्षीणां मनोश्चैव ह्याद्ये त्रेतायुगे तथा
teṣāṃ tu taptatapasā ārṣeṇopakrameṇa tu / saptarṣīṇāṃ manoścaiva hyādye tretāyuge tathā
In accord with their ardent tapas and the rishi-born mode of beginning, so too, at the very dawn of the Tretā Yuga, it was the same for the Seven Ṛṣis and for Manu.