I have been practicing a classical form of yoga for 24 years (long-enough, that is, to know I am still a beginner).
The book that started it all for me, and that remains at the core of my practice, is Swami Janakananda's beautiful text, Yoga, Tantra, and Meditation in Daily Life.
A comprehenisve, masterful instruction in classical yoga can be found in Swami Satyananda's magnum opus, A Systematic Course in the Ancient Tantric Techniques of Yoga and Kriya.
My practice of yoga informs my writing (and vice versa). An example can be found in my article in the William & Mary Business Law Reviews, Wandering Mind as Fiduciary Breach: Cognitive Duties of Corporate Directors (2024).