A copper or brass crucible was covered on the inside with a layer of wax, cleverly painted so as to resemble the ordinary metal.

Between this layer of wax and the bottom of the crucible, however, was a layer of gold dust or silver.

When the alchemist wished to demonstrate his power, he had but to place some mercury or whatever substance he chose in the crucible, heat it, throw in a grain or two of some mysterious powder, pronounce a few equally mysterious phrases to impress his audience, and, behold, a lump of precious metal would be found in the bottom of his pot.

This was the favorite method of mediocre performers, but was, of course, easily detected.
An equally successful but more difficult way was to insert surreptitiously a lump of metal into the mixture, using an ordinary crucible.

This required great dexterity, but was facilitated by the use of many mysterious ceremonies on the part of the operator while performing, just as the modern vaudeville performer diverts the attention of the audience to his right hand while his left is engaged in the trick.