Was trying to find the section in a textbook I had read about this, but this article[0] on the Dojima Market goes into a good amount of detail about this, and is a fun read.
[0]: http://disciplinas.stoa.usp.br/pluginfile.php/69204/mod_reso...
[0]: http://disciplinas.stoa.usp.br/pluginfile.php/69204/mod_reso...
It is interesting that this sort of financial instrument would have been totally impossible with water logged veggies.