 The idea evolves, states Kapila Vatsyayan, where Surya is stated to be Agni as the first principle and the seed of the universe.It is in the Brahmanas layer of the Vedas, and the Upanishads that Surya is explicitly linked to the power of sight, to visual perception and knowledge.He is then interiorized to be the eye as ancient Hindu sages suggested abandonment of external rituals to gods in favor of internal reflections and meditation of gods within, in one's journey to realize the Atman (soul, self) within, in texts such as the Brihadaranyaka Upanishad, Chandogya Upanishad, Kaushitaki Upanishad and others.