Raja Yoga, or Mental Development, by Yogi Ramacharaka the pseudonym of American attorney, occultist, author, and pioneer of New Thought William Walker Atkinson. The work was originally published in 1906 by the Yogi Publication Society. The work consists of a series of lessons, which originally appeared in a monthly format between October 1905 and Septembter 1906. They focus on using techniques such as meditation, retention of breath, and concentration to achieve ultimate goal of absorption into the cosmos. The work actually stands as a New Thought work rather than a strictly yogic one.

Raja Yoga or Mental Development (A Series of Lessons in Raja Yoga)' is a profound book authored by William Walker Atkinson, a prominent writer, and teacher in the field of self-improvement and spirituality. In this comprehensive work, Atkinson explores the principles and practices of Raja Yoga, a path that leads to mental and spiritual development. The book covers various aspects of Raja Yoga, including concentration, meditation, breath control, and the cultivation of mental powers. Through clear and accessible language, Atkinson explains the importance of mastering one's mind and emotions, and how this mastery can lead to greater clarity, peace, and self-realization. Furthermore, Atkinson delves into the nature of consciousness, the power of thought, and the connection between mind and body. The story serves as a comprehensive guide for individuals seeking to deepen their understanding of yoga and embark on a transformative journey toward self-discovery and enlightenment.

"Raja Yoga" is devoted to the development of the latent powers in Man the gaining of the control of the mental faculties by the Will the attainment of the mastery of the lower self the development of the mind to the end that the soul may be aided in its unfoldment. Much that the Western World has been attracted to in late years under the name of "Mental Science" and similar terms, really comes under the head of "Raja Yoga." This form of Yoga recognizes the wonderful power of the trained mind and will, and the marvelous results that may be gained by the training of the same, and its application by concentration, and intelligent direction. It teaches that not only may the mind be directed outward, influencing outside objects and things, but that it may also be turned inward, and concentrated upon the particular subject before us, to the end that much hidden knowledge may be unfolded and uncovered. Many of the great inventors are really practicing "Raja Yoga" unconsciously, in this inward application of it, while many leaders in the world of affairs are making use of its outward, concentrated application in their management of affairs. This book consists of twelve lessons of which students have told us that they have found it necessary to read and study each lesson carefully, in order to absorb the varied information contained within its pages.