Shiva Purana

siva.sh/siva-purana/kotirudra-samhita/3/8

तत्र च ब्रह्मणः पुत्रो ह्यत्रिनामा ऋषिः स्वयम् ।। तपस्तेपेऽति कठिनमनसूयासमन्वितः ।। ८ ।।

sanskrit

There was a sage named Hyatri himself, the son of Brahma. He performed very difficult austerities without envy.

english translation

tatra ca brahmaNaH putro hyatrinAmA RSiH svayam || tapastepe'ti kaThinamanasUyAsamanvitaH || 8 ||

hk transliteration by Sanscript