History's Mysteries

It's every collector's fantasy. An afternoon in an antique shop produces a gem that lights up a dim piece of the past. This was the seductive story on offer in Beijing last week when lawyer and collector Liu Gang unveiled a map that, he says, proves the Chinese had detailed knowledge of world geography long before the voyages of Columbus, Magellan and da Gama brought such insights to Europe. This "Overall Map of the Geography of All Under Heaven," which Liu says he bought for $500 in Shanghai's Dongtai Road Antique Market, includes notes claiming it was drawn in 1763 as...