Saṃkhyāvarta (संख्यावर्त्त): Commencement of Yajña at the Dawn of Tretāyuga
श्रूयन्ते हि तपःसिद्धा ब्रह्मक्षत्रादयो ऽनघाः / प्रियव्रतोत्तानपादौ ध्रुवो मेधातिथिर्वसुः
śrūyante hi tapaḥsiddhā brahmakṣatrādayo 'naghāḥ / priyavratottānapādau dhruvo medhātithirvasuḥ
Indeed it is heard that blameless brahmins, kṣatriyas, and others attained perfection through tapas—Priyavrata, Uttānapāda, Dhruva, Medhātithi, and Vasu.