Analysis of information sources in references of the Wikipedia article "控火" in Chinese language version.
The "coal" is a piece of spongy platinum which bears a close resemblance to a lump of half burnt coal, and is palmed in the hand, as a prestidigitateur conceals a coin, a pack of cards, an egg, or a small lemon. The medium or magician advances to the grate and pretends to take a genuine lump of coal from the fire but brings up instead at the tops of his fingers, the piece of platinum.
