I know! Have a currency directly fixed to integers. Say, integers below X, where X is some reasonable granularity for the foreseeable future. There are exactly so many of them, and bank notes already have serial numbers, so it's technically possible! :>

People still keep searching for and mining gold. That was silly two thousand years ago, but they have the excuse that they didn't know better. I read that current methods used for mining gold in some countries (e.g. Argentina) are especially hazardous for public health and the environment of local populations.