It is right to notice that Greco-Roman societies knew advanced economic capitalism, since, on this point of view, Middle Age was a regressive period. The money was a sign of power and richness, and a safety to pay ransoms - the natural risks for these warriors. Feudal ones really had only servile poeple as a capital and they could not draw any profit from their gold. The Renaissance was the resurgence of ancient thought. It was joined again with capacity of abstraction in such matters as economy, technical sciences and arts.
Powers of money reconstitute themselves.
The Ancient use of currency has been reviving thanks to the Renaissance. An invention which upsets time and space. At all events, they soon use gold instead of animals. So they were compelled to weight each pieces of metal. From there, to count pieces was sufficient, it was useless to weigh.