The Wealth of Nations by Part 1 Chapter 11 Page 118

In an ancient manuscript of the Regiam Majestatem, an old Scotch law book, there is a statute of assize in which the price of bread is regulated according to all the different prices of wheat, from tenpence to three shillings the Scotch boll, equal to about half an English quarter.

Three shillings Scotch, at the time when this assize is supposed to have been enacted were equal to about nine shillings sterling of our present money. Mr. Ruddiman seems to conclude from this, that three shillings was the highest price to which wheat ever rose in those times, and that tenpence, a shilling, or at most two shillings, were the ordinary prices. Upon consulting the manuscript, however, it appears evidently that all these prices are only set down as examples of the proportion which ought to be observed between the respective prices