Hi Housewright:
I suggest that in the days before modern measurement long timbers were easily laid out with measuring poles as i noted above.
For instance at the planning stages of the framing of a timberstructure, you would mention to the tradesman, that you would like him to plan the raising of a 3 bay barn, that would include a threshing floor, one full hay storage bent, and one stable bent with hay storage overhead.
Approx measurements would be discussed, and then when the time to lay out the long plates, mud sills and cross girts, he would just measure off the squared timbers using the correct number of repeated measurements using an appropriate measuring pole. Exact inches were not a factor at this point, what did matter was that all the timbers were the same length.
If you carefully measure old timber structures they very seldom will be exact inches and feet, but they will be all similar in length
I hope this helps
NH