Over a thousand years ago, natives would mine enormous chunks of limestone and carve them into gigantic circular discs.

I'm talking REALLY big… a typical disc would be 5 to 10 feet in diameter, over a foot thick, and weigh several tons.

They called them 'Rai Stones', and they were actually used as currency. Curiously, an indiviaul rai would be valued not based on its weight or size, but based on its story.

If many people had been killed transporting it, or if the stone had once belonged to a famous warrior, the rai would be worth more. So it was a bit of a collectible as well as a form of money.

Needless to say, the sheer size of these stones meant that they wouldn't be moved very often. Everyone on the island just sort of knew who owned each rai, like a primative form of Bitcoin's blockchain.

The polar opposite of this is the paper money system, something that has its origins in the Han Dynasty over 2,000 years ago.

It wasn't quite paper, but the ancient Chinese experimented with leather-skinned money as early as the second century BC.