Patanjali Yog Sutra one of the oldest Indian text on traditional yoga. Till date no one knows about the author of the book. It is believed that it was written in 400 CE. The book consist of four chapters which contains 196 aphorisms. The first chapter is samadhi pada that consists of 51 sutras. Samadhi refers a blissful state where yogi is absorbed into one. This is the basic step to reach the depth of the mind.
The second chapter of the book focuses on Sadhana Pada. This chapter consists of 55 sutras. The word refers to practice or discipline. Here the author focuses on two yogas – Ashtanga yoga and Kriya Yoga. Third and fourth chapter are Vibhuti pada and Kaivalya Pada respectively. Former consist of 56 sutras and latter consists of 34 sutras respectively.