
This seminal work is a classical text on yoga theory and practice written some time between the 2nd century BCE and the 4th century CE. It starts with a chapter that talks about the necessities for an aspirant to liberation. Chapter Two describes the method to attain this. Patanjali's eight principles are in this chapter and at the end of the chapter the author has added a section in which Adi Sankara extends Patanjali's eight principles to fifteen. Chapter three describes various powers and chapter four reaches to the ultimate truth.