On April 2, 1792, U. S. Secretary of the Treasury Alexander Hamilton reported to Congress the precise amount of silver found in Spanish milled dollar coins in common use in the States. As a result, the United States Dollar was defined as a unit of weight equaling 371 4/16th grains (24.057 grams) of pure silver, or 416 grains of standard silver (standard silver being defined as 1,485 parts fine silver to 179 parts alloy). It was specified that the “money of account” of the United States should be expressed in those same “dollars” or parts thereof.
371.25 gr = 0.848572 oz = 24.0566 g.
On April 8th silver closed at $40.93/oz.
That means it would take 34.73 Federal Reserve Notes to buy 1 United States Dollar's worth of silver.