Today I learnt that the island of Yap (it's real - it is now part of the Federated States of Micronesia) used to have as currency carved stoned so big you couldn't move them. True story. I think.
Its coins, the rai, look like stone doughnuts. Some are fairly portable, the size of actual doughnuts, but others weigh as much as a couple of cars. The process of producing these things, 250 miles across the sea in the quarries of Palau, used to be a gigantic effort – a Victorian naturalist witnessed a tenth of Yap’s adult male population digging these things out of the ground and sailing them back to Yap.