This book relates to the system of Rajayoga as enunciated by Patanjali and explained by his commentators - Vyasa, Vacaspati, Vijnanabhiksu and others. It deals with the foundation of yogic practices, their philosophical, psycho-logical, cosmological, ethical and religious doctrines. It comprises the essential features of the yoga system with other systems of philosophical thought, and establishes its affinity with the system of sankhya.