The Vedic fire for performing yajna was not ignited with ordinary matches or similar devices. Rather, the Vedic sacrificial fire was ignited by the aranis, or two sacred pieces of wood, which produced fire by friction with a third. Such a fire is necessary for the performance of yajna. If successful, a yajna will fulfill the desire of its performer. Thus Pururava took advantage of the process of yajna to fulfill his lusty desires. He thought of the lower arani as Urvasi, the upper one as himself, and the middle one as his son. A relevant Vedic mantra quoted herein by Visvanatha Cakravarti Thakura is sami-garbhad agnim mantha. A similar mantra is urvasyam urasi pururavah. Pururava wanted to have children continuously by the womb of Urvasi. His only ambition was to have sex life with Urvasi and thereby get a son. In other words, he had so much lust in his heart that even while performing yajna he thought of Urvasi, instead of thinking of the master of yajna, Yajnesvara, Lord Visnu.