The Rai are large stone disks used as a currency until the 20th century on island Yap in the Western Pacific.  As currency, due to some similarities to way of using, they can be looked at as a sort of pre-Bitcoin so lets see why.

As they had extraordinary size, Rai stones were not moved when spent, but simply changed owners. Every transaction was ‘recorded’ orally within the small community – so the stone’s ownership history became common knowledge.  The only thing that mattered was the “transaction history“ or „ledger”. The same way as in crypto currencies world there is a blockchain that is nothing else than ledger or transaction history!

For example, once one stone was dropped by the canoe transferring it and it sank. No matter to the fact that nobody had access to it any more, that stone was still deemed to be money. This example is very important as it shows a naturally occurring use of a ledger of transactions – which was  shared orally between the inhabitants and attributed ownership and property without a single stone moving, just because everyone agreed on it.

Rai stone on display at the Bank of Canada Currency Museum in Ottawa, Canada.   Source: https://en.wikipedia.org/wiki/Rai_stones