One ounce of sugar? That'd be a pretty flat brew...
...2.4-2.6 volumes is a pretty good all around range, but feel free to experiment a bit based upon personal taste and style recommendations.
This KotMF calculator will provide you with guidelines based upon style.
There are some old British brewing books where the brewers added NO priming sugar, just bottled and walked away, but it would take a hellova lot longer than 3 weeks for the beer to carb up then, especially at cellar temps. It was probably the practice for long sea voyages in the IPA days, to let it carb very low and naturally, especially if the beer was being pushed with a beer engine...I imagine some brewers though who have come upon those old books forget that part about the amounts being used for cask conditioned beers...Though I do think some of the IPA's did travel in corked bottles.
I thought I heard some bottles were brought up from a shipwreck and sold at auction...Methinks they would be purposefully under carbed/natural bottle carbed to prevent them from "bombing" while they traveled as cargo, where the temps in holds would probably go all over the place, near freezing to over a hundred degrees...you wouldn't want them to be that primed up or else they'd blow.
IIRC I ran the numbers a year ago using an ordinary bitter as the base beer, and came up with some sugar amounts/per volumes of Co2 that were practically microscopic...One of the volumes actually came up as a "-" negative amount of priming sugar to hit the lowest end of the range for the style of the beer.
In the 21st century, especially in the states, we tend like our beer more carbed up then they did back then...I think I heard the same for England, despite camra...The actual carbed levels of the real ales are a little higher now than their historical ancestor batches.
Even looking at a style volume range on beersmith, I will tend to hit the high, or the mid end of the range, as opposed to low end volumes..though I just had an ordinary bitter that I purposefully bottled at the bottom end, and though it has little bubbles it is still carbed and conditioned (actually it's been conditioning since July to let it mellow some, I used aromatic malt for the first time, and wasn';t sure I liked the profile.)