The first time I bought Black Powder I was a small boy in 1957 and wanted to know how many shots from 1 pound my 45 Cal flint squirrel rifle would shoot. I remember the gun shop salesman telling me, “You should get 100 Deer loads or 200 squirrel loads because you use less powder for squirrels.”
The powder was 2F and I had a small wooden mortar and pestle for making fine primer powder. Yea, I had a good Elmer and wish he had lived longer.
Modern conclusion: I currently use a 70 gr round ball charge in 45 Cal muzzle loader rifles. That is 100 shots per pound. Beginners in muzzle-loading are often conflicted and asking questions about what the real old charge recommendation was. Today there is all kinds of recommended loads for muzzle loaders in manuals and from powder and bullet makers.
I did use a powder measure as a boy. It was a 45 Colt pistol empty fired cartridge case. That was the only charge I fired and I honestly couldn't couldn't tell you what the weight of that measured load was, but it sure shot well. I didn't start actually weighing charges of BP until I was 16 and had a scale and a Big Game license.