Anushasana Parva 40.49

Giving his best consideration to these points of virtue, thinking of all the Vedas and their branches and with eye directed to the penances which his preceptor had and which he himself also was possessed of, and having settled in his mind, with a view only to protect the lady, to enter her body by Yogapower, Vipula of Bhrigu's race, took great care (for accomplishing his object. Listen now to me, O king, as I recite to you what he did.