Mbh 12.351.2a

"Vaisampayana said, 'In the speculations of the Sankhya and the Yoga systems many Purushas have been spoken of, O jewel of Kuru's race. Those that follow these systems do not accept that there is but one Purusha in the universe.[1916] In the same manner in which the many Purushas are said to have one origin in the Supreme Purusha, it may be said that this entire universe is identical with that one Purusha of superior attributes. I shall explain this now, after bowing to my preceptor Vyasa, that foremost of Rishis, who is conversant with the soul, endued with penances, self-restrained, and worthy of reverent worship. This speculation on Purusha, O king, occurs in all the Vedas. It is well known to be identical with Rita and Truth. The foremost of Rishis, viz., Vyasa, has thought upon it. Having occupied themselves with reflection on what is called Adhyatma, diverse Rishis, O king, having Kapila for their first, have declared their opinions on the topic both generally and particularly. Through the grace of Vyasa of immeasurable energy, I shall expound to thee what Vyasa has said in brief on this question of the Oneness of Purusha. In this connection is cited the old narrative of the discourse between Brahma, O king, and the Three-eyed Mahadeva. In the midst of the Ocean of milk, there is a very high mountain of great effulgence like that of gold, known, O monarch, by the name of Vaijayanta. Repairing thither all alone, from his own abode of great splendour and felicity, the illustrious deity Brahma used very often to pass his time, engaged in thinking on the course of Adhyatma. While the four-faced Brahma of great intelligence was seated there, his son Mahadeva, who had sprung from his forehead encountered him one day in course of his wanderings through the universe. In days of yore, the Three-eyed Siva endued with puissance and high Yoga, while proceeding along the sky, beheld Brahma seated on that mountain and, therefore, dropped down quickly on its top.