The Sibyl, questioned on what was a Philosopher, answered: “It is that which can make glass.” Apply you to manufacture it according to our art, without taking account of the processes of glassmaking too much. The industry of the potter would be more instructive to you; see the boards of Piccolpassi, you will find of them one which represents a dove whose legs are attached to a stone. Don’t you have, [...], to seek and find the mastery in a volatile thing? [...] Thus make your mud, then your compound; seal carefully in manner that no spirit can be exhaled; heat the whole according to art until complete calcination. Give the pure portion of the powder obtained in your compound, that you will seal in the same mud.