The Vedic fire for performing yajña was not ignited with ordinary matches or similar devices. Rather, the Vedic sacrificial fire was ignited by the araṇis, or two sacred pieces of wood, which produced fire by friction with a third. Such a fire is necessary for the performance of yajña. If successful, a yajña will fulfill the desire of its performer. Thus Purūravā took advantage of the process of yajña to fulfill his lusty desires. He thought of the lower araṇi as Urvaśī, the upper one as himself, and the middle one as his son. A relevant Vedic mantra quoted herein by Viśvanātha Cakravartī Ṭhākura is śamī-garbhād agniṁ mantha. A similar mantra is urvaśyām urasi purūravāḥ. Purūravā wanted to have children continuously by the womb of Urvaśī. His only ambition was to have sex life with Urvaśī and thereby get a son. In other words, he had so much lust in his heart that even while performing yajña he thought of Urvaśī, instead of thinking of the master of yajña, Yajñeśvara, Lord Viṣṇu.