The Wealth of Nations by Part 1 Chapter 11 Page 105

century, what was reckoned the reasonable and moderate, that is the ordinary or average price of wheat, seems to have sunk gradually to about one-half of this price; so as at last to have fallen to about two ounces of silver, Tower weight, equal to about ten shillings of our present money.

It continued to be estimated at this price till about 1570.

In the household book of Henry, the fifth Earl of Northumberland, drawn up in 1512, there are two different estimations of wheat. In one of them it is computed at six shillings and eightpence the quarter, in the other at five shillings and eightpence only. In 1512, six shillings and eightpence contained only two ounces of silver, Tower weight, and were equal to about ten shillings of our present money.