Markandeyapurana 52.25

52.25

ṣaṣṭiryāni sahasrāṇi ṛṣīṇāmūrdhvaretasām /
ūrjāyāntu vasiṣṭhasya saptājāyanta vai sutāḥ //

Now Sannati was the wife of Kratu[11]; she gave birth to the Bālikhilvas, the sixty thousands, which they are, of ṛṣis who live in perpetual chastity.[12]

Now seven sons were born of Urjā by Vasiṣṭha,[13] Rajas, Gātra and Urdhvabāhu, and Sabala, and Anagha, Sutapas, Śukta; all these are well-known as seven Ṛṣis.