"Fermentation is the incorporation of a fermenting substance with a substance which is to be fermented. For even as a small modicum of ferment, or yeast, can leaven a large mass of flour so does the chemical ferment assimilate itself to the thing that is to be fermented. Whatsoever be the nature of the ferment, of such is the fermented matter. By ferment the philosophers understand a true body and a true matter, which, united to its proper Mercury, convert it into the nature thereof."

-Rulandus, M. (1612) A Lexicon of Alchemy.