The Yoga Sutras of Patanjali are on Perception. They are really deep. It was very nice to see them in light of psychology through Rohit Mehta's lens. He has done good justice in maintaining the essence of using psychological terms. When I have to recommend the commentary for an appropriate understanding of the Yoga Sutra, I always suggest this book to those who feel not ready for Hariharanand Aranya's commentary. i have personally gained a lot from reading it.