The Rai Stones are huge stone wheels used as currency on the island of Yap

Economists love it because it helps answer this really basic question: What is money?

It also helps understand the value of bitcoins or crypto currency

"Rai were considered extremely valuable, but given their size, weight, and relative fragility, they were not typically moved after being placed in a specific location," Fitzpatrick and co-author Stephen McKeon explain in a new study exploring the similarities.

"As a result, if a rai were gifted or exchanged, the new owner(s) of a disk may not have lived in close proximity to it. To ensure that ownership was known and indisputable, an oral ledger was used within communities to maintain transparency and security."

According to the researchers, this oral ledger – told through stories shared by the Yapese and passed down over generations – helped the community to record and communicate changes in ownership of the rai, for things like wedding gifts, political enticements, or even paying ransoms.