Alchemy is a precursor to modern chemistry which was widely practiced all over the world through the 1800s, when more modern chemistry began to displace it. This discipline involved a study of the chemical properties of various substances, with a mystical bent. The main principle being to transform ordinary base metals into Gold.
Spiritual alchemy, can be likened to this, as in transforming the basic material of man, mind body and spirit and transforming it to its purest and highest form. The gold of alchemy was simply hastened perfection, inner and outer, the divinization of matter and man.