The Wealth of Nations by Part 4 Chapter 3 Page 40

To prevent the stock-jobbing tricks which those opposite interests might sometimes occasion, the bank has of late years come to the resolution to sell at all times bank money for currency, at five per cent agio, and to buy it in again at four per cent agio. In consequence of this resolution, the agio can never either rise above five or sink below four per cent, and the proportion between the market price of bank and that of current money is kept at all times very near to the proportion between their intrinsic values. Before this resolution was taken, the market price of bank money used sometimes to rise so high as nine per cent agio, and sometimes to sink so low as par, according as opposite interests happened to influence the market.

The Bank of Amsterdam professes to lend out no part