Arthur Edward Waite 
What is Alchemy? 

The exaltation of the base nature in man, by the development of his latent powers; the purification, conversion, and transmutation of man; the achievement of a hypostatic union of man with God. Not only was all this the concealed aim of Alchemy, but the process by which this union was effected, veiled under the symbolism of chemistry, is the process with which the literature is concerned, which process also is alone described by all veritable adepts. The man who by proper study and contemplation, united to an appropriate interior attitude, with a corresponding conduct on the part of the exterior personality, attains a correct interpretation of Hermetic symbolism, will, in doing so, be put in possession of the secret of divine reunion, and will, so far as the requisite knowledge is concerned, be in a position to encompass the great work of the Mystics. The power which operates in the transmutation of metals alchemically is, in the main, a psychic power. That is to say, a man who has passed a certain point in his spiritual development, after the mode of the Mystics, has a knowledge and control of physical forces which are not in the possession of ordinary humanity.