To counterfeit EMERALDS: Take of natural crystal, four ounces; of red lead, four ounces; verdigris, forty-eight grains; crocus martis, prepared with vinegar, eight grains: let the whole be finely pulverized and sifted: put this into a crucible, leaving one inch empty: lute it well, and put it into a potter's furnace, and let it stand there as long as they do their pots. When cold, break the crucible; and you will find a matter of a fine emerald colour, which, after it is cut and set in gold, will surpass in beauty an oriental emerald.