Power is necessary and should be developed; but when man is anxious to develop power, either of body or of mind, he ought to remember that the will power is behind it all; that if the will is developed, the physical and mental power can easily be developed. The will power governs the body and the mind.  - Hazrat Inayat Khan, Mastery, p. 211

In the East I have seen a man lifting a heavy stone on one finger. One might wonder how that can be possible, but it is the power of the will alone which sustains the heavy stone; the finger is only an excuse. - Ibid, p. 170