The great Indian sage, Patanjali’s Yoga Sutra was written some one thousand six hundred years ago (circa AD 300 – 400). The yoga systematised by Patanjali is commonly known as Raja Yoga. The path of Raja Yoga is chiefly psycho-physical. 

The psychological system of a human being is made to undergo severe training so as to enable it to respond to the spiritual entity within. This spiritual entity referred here is the Purusha (real self) which has to be librated from the Prakruti.

This classical work is divided into four Padas (chapters). They describe the science and philosophy of yoga in an erudite and intuitive style. The four chapters are titled thus: 

1.   Samadhi Pada(on contemplation)
2.   Sadhana Pada(on practice)
3.    Vibhuti Pada(on properties and powers)
4.    Kaivalya Pada(on liberation) 

Together they contain 196 terse aphorisms on yoga.