who stated that the prosperity of a nation depended on a large supply of gold and silver?

Answer 1

Piles of people, there are numerous folk that believe that a nation's currency needs to be connected to stores of precious metals. There was a deviation a few centuries back, which moved monetary thinking beyond mere gold and silver backing, it was called mercantilism, but even they wanted a precious metal floor for the value of the currencies used in trade.

Ludwig von Mises and Friedrich von Hayek are two economic champions of this with a firmer grasp and a great deal more realistic sophistication.

Walter Block's article discusses the gold standard with particular interest to Hayek's stand.