Money from the docu about energy from a mining company
Discussion
Rai Stones
https://en.m.wikipedia.org/wiki/Rai_stones
They're mentioned many times because it's the first public ledger, very similar to how #Bitcoin works. The coin isn't moving, just the ownership changes - the stones worked the same way.
Seems rather impractical to me. Just one place to exchange and come to an agreement. It probably only worked for a group of 20 max.