The practice of making casts of engraved gems, and thus circulating their images, was common from ancient times, and became widespread among Roman connoisseurs in the 18th century. The sale of casts of gems boomed as they became an essential souvenir of the Grand Tour, and firms set up in business to sell boxes of trays with identifying lists, or even casts in boxes disguised as books for the library shelf. The most comprehensive of casters was the Scotsman James Tassie and later his nephew William Tassie, whose catalogue eventually encompassed over 20,000 items.