Doctrine and Practice of Yoga by Swami Mukerji

According to Wikipedia: "Yoga is the Hindu practice of physical, mental, and spiritual discipline, originating in ancient India. The goal of yoga, or of the person practicing yoga, is the attainment of a state of perfect spiritual insight and tranquility while meditating on the Hindu concept of divinity or Brahman. The word is associated with meditative practices in Hinduism, Jainism, and Buddhism."