Raja Yoga is also known as “Classical Yoga” og “Royal Union Yoga. The foremost concern is the discipline of the mind, the postures, asanas, are the carriage. This book “Raja Yoga or Conquering the Internal nature” goes into details about breathing techniques, concentration and themes like non-attachment. From the foreword:
“The goal is to manifest this divine within, by controlling nature, external and internal. Do this either by work, or worship, or psychic control, or philosophy, by one, or more, or all of these—and be free. This is the whole of religion. Doctrines, or dogmas, or rituals, or books, or temples, or forms, are but secondary details.”