The stone wheel money of Yap is called "fei." An American anthopologist, William Henry Furness II, spent several months on the island in 1903 and described some interesting things about the use of fei. They weren't all giant -- some of the small limestone money was about the size of a saucer. These smaller "coins" were everyday money, used to buy fish or pigs.

The bigger ones, despite the holes carved in the center to make moving easier, were almost never moved -- if a transaction took place that changed the ownership of one, it stayed where it was and people just acknowledged that it belonged to someone else now. In fact, one of the wealthiest Yap families owned a fei that no one had seen in generations -- it sank with the raft it was being towed on when a storm came up during moving to Yap from its source. No one ever doubted the truth of the man who said he'd cut such a huge stone, and its purchasing power at the bottom of the ocean remained as valid as that of a checking account.

In 1898, the German government bought the Caroline Islands from the government of Spain, its former colonists. The Germans wanted to build roads on Yap, but the natives were not interested in helping. At least not until they were introduced to a version of taxation; the German officials marked the most valuable fei with a symbol indicating they were German property. Immediately, the Yapese were willing to build roads to German satisfaction, and were paid for so doing with their own former property.

Bernstein, Peter L. The Power of Gold: The History of an Obsession. New York: John Wiley & Sons, 2000.