There was a gaṇa (gana; genus) of the ṛṣi(s) (rishi; sages) called Ūrja (Urja). They were the sons of Brahmā (Brahma). According to Śivapurāṇa (Sivapurana), they preached dharmaśāstra (dharmasastra; scriptures of righteous codes) during the time of Vaivasvata Manu.