Shiva Purana
गौतमोऽपि स्वयं तत्र वरुणार्थे तपश्शुभम् ॥ चकार चैव षण्मासं प्राणायामपरायणः ॥ ८ ॥
Gautama himself performed an suspicions penance of Varuṇa for six months engrossed in Prāṇāyāma.
english translation
gautamo'pi svayaM tatra varuNArthe tapazzubham ॥ cakAra caiva SaNmAsaM prANAyAmaparAyaNaH ॥ 8 ॥
hk transliteration by Sanscript