There is profuse richness in the records of yoga that we find in the Vedic Samhitas and Upanishads, and also in the Brahmanas and Āranyakas to some extent. The exposition that is presented is somewhat detailed, and it is likely to appear much too repetitive. But considering the immense richness of the original material, what has been presented, may appear to some, too scanty and too selective. Our object is to present sufficient material that might bring out not only the richness of the yogic experiences that we find in "humanity's earliest records of yoga but also to show the patterns and systems of yogic methods which had come to be developed.
There have been many philosophical treatises that aim at commenting and explaining the contents of the Vedas and Upanishads. The related philosophical treatises present :controversies that reflect rival philosophical systems. In our presentation, we have avoided philosophical interpretations, since our aim is to present significant passages that relate to yogic methods and yogic realizations, leaving the task of philosophical discussions to researchers who may be interested in such discussions.
In brief, our aim is to show that the methods of yoga are psychological in character and that they relate to detailed cultivation of the psychological powers of cognition,