Yogi Ramacharaka 
A Series of Lessons in Gnani Yoga (The Yoga of Wisdom) [EPUB ebook] 

‚The Yogi Philosophy may be divided into several great branches, or fields. What is known as ‚Hatha Yoga‘ deals with the physical body and its control; its welfare; its health; its preservation; its laws, etc. What is known as ‚Raja Yoga‘ deals with the Mind; its control; its development; its unfoldment, etc. What is known as ‚Bhakti Yoga‘ deals with the Love of the Absolute-God. What is known as ‚Gnani Yoga‘ deals with the scientific and intellectual knowing of the great questions regarding Life and what lies back of Life-the Riddle of the Universe.‘ So begins ‚A Series of Lessons in Gnani Yoga (The Yoga of Wisdom)‘ by Yogi Ramacharaka.