Query: How many grains of pure silver were meant to be in a single dollar?
Context: In 1792 the U.S. Congress adopted legislation titled An act establishing a mint, and regulating the Coins of the United States. Section 9 of that act authorized the production of various coins, including "DOLLARS OR UNITS—each to be of the value of a Spanish milled dollar as the same is now current, and to contain three hundred and seventy-one grains and four sixteenth parts of a grain of pure, or four hundred and sixteen grains of standard silver". Section 20 of the act provided, "That the money of account of the United States shall be expressed in dollars, or units... and that all accounts in the public offices and all proceedings in the courts of the United States shall be kept and had in conformity to this regulation".