Sankhya, among the most ancient Vedic darshanas, is detailed in the essential text, Sankhya Karika, authored by the sage Isvara Krishna. Yoga and Sankhya are closely related. The Yoga Sutra is an expansion of Sankhya, and Krishna declares in the Bhagavad Gita that one must view Sankhya and Yoga as one. Sankhya provides the framework and fundamental theory of how to reach the ultimate transcendental state that yoga points us toward. Yoga expands on the practices.