A little over a year ago, Daniel Crouch, one of the foremost dealers of rare books, maps, and atlases in the world, came into possession of a 19th-century map. It had been drawn by a man named Gregor MacGregor. “The first thing you need to know about Gregor MacGregor, from the Clan Gregor, is he’s improbably named,” says Crouch. “The second is that his story is so improbable, but, trust me, everything I’m about to tell you is true.” The map depicts the Central American monarchy of Poyais, an oasis…
