-Papa! what's money?
-What is money, Paul? Money?
-Yes, what is money?
-Gold, and silver, and copper. Guineas, shillings, half-pence. You know what they are?
-Oh yes, I know what they are. I don't mean that, Papa. I mean what's money after all?
Little Paul Dombey, Dombey and Son, by Charles Dickens (1848)


What part of the total money supply is physical cash, i.e. coins and banknotes? How did that ratio evolve in Greece from 1836 to 1999?