Madhu-Vidya (Nectar of the Sun): as described in the Upaniṣad

Abstract: The natural sun-light is a symbol of spiritual light. Brahman is the real Sun of the universe; and the natural sun is the phenomenal form of Brahman. The Puruṣa in the sun, whose counterpart is the Puruṣa in the right eye, was worshiped by the Vedic seers. In the Praśnopniad Ṛṣi Paipallāda said that the sun is the life and described the activities of sun and supreme qualities of the sun. By these activities all living non-living objects are visible. The Madhu-vidyā occupies a unique in the Upaniṣadic scheme of due to its supremely hidden significance and peculiarly mystic presentation. It has got two different versions; one in the Chāndogya and another in the Bṛhadāraṇyaka depict a long series of cause and effect, showing their mutual interdependence and finally lead to the Ātman which is shown to be the Supreme Source of everything else.