Yoga is one of the Six Systems of Vedic philosophy, and Yoga Sūtra is the oldest and most authoritative text on this philosophy. This book translates and comments on this ancient text. The text begins by describing how conscious experience begins in the Chitta, which is the repository of our past experiences, accumulated over many lifetimes. From this historical record of past experiences, thoughts and desires are produced automatically, which the soul falsely considers as its creations, and thus becomes a slave to its past. The purpose of Yoga is to destroy this historical record and liberate the soul from the bondage of its past. To achieve this goal, the Yoga Sūtra presents an eight-step process comprising Yama, Niyama, Āsana, Prāñayāma, Pratyāhāra, Dhārana, Dhyāna, and Samādhī. The steps of meditation called Dhārana and Dhyāna are stated to be the surrender to the form of the Lord called Paramātma in the heart. This surrender-called īśvara prānidhāna-is the perfection of Yoga. All previous steps are presented as the means to help the practitioner of Yoga meditate unflinchingly. The text presents eight-fold mystical perfections called Siddhis, gained by a Yogi who has mastered the control of Prāña. This book discusses the details of these mystical perfections and how they rest upon an alternative understanding of matter. They enable a Yogi to become light or heavy, small or big, walk on fire, water, or air, travel to distant places in a moment, or change his or her body instantly.