Bernard Trevisan
"The first thing required for the secret Science of the Transmutation of Metals, is the knowledge of Matter, from which come the Quicksilver of the Philosophers and their Sulphur, from which they make and constitute their divine Stone. The Matter, from which this sovereign Medicine is extracted, is Gold, very pure, Silver very fine, and our Mercury or Quicksilver, which you see daily altered and changed by artifice into Nature of a white and dry Matter, in the manner of Stone, from which our Quicksilver and our Sulfur are raised and extracted with strong ignition, by a repeated destruction of this matter, by resolving and sublimating.
In this Quicksilver are Air and Fire, which cannot be seen with bodily eyes, so rare and spiritual are they: Which belies those who believe that the four Elements are really and visibly separated in the Work, each apart; but they have not well conceived the nature of Things; Because, one cannot give the simple Elements; we know them only by their operations and effects, which are in the lower Elements, namely in the Earth and in the Water, according as they are altered from closed and gross nature, by which they are changed from Nature into Nature. Gold and Silver, according to the Doctrine of all the Philosophers are the Matter of our Stone. Verily, says Hermes, his Father is the Sun, and his Mother is the Moon.
What embarrasses the most is to know what the Third Component is; that is, what is this Quicksilver, from which we make our Compost with Gold and Silver. To know this, it should be noted that the Work of the Philosophers is divided principally into two Parts. The Philosophers divide the second Part into the accomplished White Stone, and the equally accomplished Red Stone." [The Abandoned Word by Bernard Trevisan, c. 1618]
Manly Palmer Hall
"What is the meaning of transmutation as used by Occultists?
Ans. Transmutation is that chemical change which takes place in organisms when the integral parts are vitalized by higher rates of vibration. The alchemist taught that to be wise, man must learn to transmute base metals into gold. This meant that he must acquire the knowledge of how to transmute his lower nature and his lower bodies into vehicles fine enough to respond to the subtle influences of his spiritual nature. He must transmute all of his forces so that they shall serve good instead of evil. [Special Class in Secret Doctrine in Appreciation of H.P.B. (Madame Blavatsky) by Manly Palmer Hall]