Blavatsky
Original sense
Yoga means union of the lower with the higher, and she praised raja-yoga — ethical and mental discipline aimed at that union. She repeatedly condemned public hatha-yoga (postures, forced breath, kumbhaka) as a physical ordeal that could awaken powers without wisdom. The Voice of the Silence is her yoga book, and it contains no asana.
Hatha-yoga, at best, results in a purely psychic and physiological training… Râja-yoga is the real science of the development of the spiritual inner man.
Vivekananda, not Blavatsky, is the main door by which yoga entered American popular religion. Her contribution was to make ‘yoga’ mean an occult path of discipleship in English esotericism before the mat existed.