Thus we see that Pranayama includes all that is true of spiritualism even. Similarly, you will find that wherever any sect or body of people is trying to search out anything occult and mystical, or hidden, what they are doing is really this Yoga, this attempt to control the Prana. You will find that wherever there is any extraordinary display of power, it is the manifestation of this Prana. Even the physical sciences can be included in Pranayama. What moves the steam engine? Prana, acting through the steam. What are all these phenomena of electricity and so forth but Prana? What is physical science? The science of Pranayama, by external means. Prana, manifesting itself as mental power, can only be controlled by mental means. That part of Pranayama which attempts to control the physical manifestations of the Prana by physical means is called physical science, and that part which tries to control the manifestations of the Prana as mental force by mental means is called Raja-Yoga.