Sandbanks

For a brief period in the 11th century, Spain, at that time short on gold, toyed with the idea of using sand as currency. The scheme was well underway, with over 100 sandbanks already in place across the empire, when it was found that many caribbean countries would stand to be significantly wealthy - with an order of magnitude more wealth than Spain itself. The idea was thus abandoned, and the banks thrown into the ocean where they disturb sailors to this day.

_{All content copyright Tom Crowley}