The Wealth of Nations by Part 1 Chapter 11 Page 117

the price of barley, from two shillings to four shillings the quarter.

That four shillings, however, was not considered as the highest price to which barley might frequently rise in those times, and that these prices were only given as an example of the proportion which ought to be observed in all other prices, whether higher or lower, we may infer from the last words of the statute: et sic deinceps crescetur vel diminuetur per sex denarios. The expression is very slovenly, but the meaning is plain enough: “That the price of ale is in this manner to be increased or diminished according to every sixpence rise or fall in the price of barley.” In the composition of this statute the legislature itself seems to have been as negligent as the copiers were in the transcription of the others.