Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The term Rāja Yoga is a retronym, introduced in the 15th-century Hatha Yoga Pradipika to distinguish the school based on the Yoga Sutras of Patanjali from the more current school of Hatha Yoga expounded by Swami Swatmarama. The term was later used to describe the entirely unrelated meditation practice of the Brahma Kumaris. Raja Yoga is sometimes referred to as Aṣṭānga (eight-limbed) yoga because there are eight aspects to the path to which one must attend. Patanjali himself called his system of yoga 'Kriya Yoga' as is known in his first sutra of the second chapter: Tapas svadyaya ishvarapranidhanani kriya yogah (2:1), "Discipline, insight, and devotion are the pillars of Kriya Yoga".