"Yoga Darshan" which is also known as ''Yoga Sutra" also is the first-ever book on yoga. Though the science of yoga was discovered very before the inception of this book and it has been mentioned in every Indian scripture including Vedas and Upanishads but it is very scattered. Yoga Darshan is the first yoga book that is fully focused on yoga. Maharshi Patanjali, one of the greatest sage wrote or compiled it around third BC. This is one of the most classic, precise and brief book ever written on yoga.
This classic book has four chapters. The first chapter "Samadhi Pada" is devoted to those spiritual practitioners who are very advanced in their practice. In it, he defines yoga as a state where all the mental fluctuations stop. He precisely describes here five types of fluctuations and the way this vrittis (fluctuations) are made. Apart from it, he mentions the two most advanced techniques- practice and detachment for restraining this vrittis. The second chapter is devoted to the moderate and lowest type of practitioners. This is kriya yoga and ashtanga yoga. Ashtanga yoga or eight limbs of yoga is a very easy way for common people. The third chapter is on the supernatural powers achieved by ashtanga yogi. There are many types of yoga Siddhis which are achieved by ashtanga yoga practitioners. The last chapter is "Kaivalya Pada" which is about the highest goal of yoga. Kaivalya word means to get established in one's own self after practicing supreme detachment- para vairagya.