OO canvas

[geopiet]

In his book titled "Camp and Trail" published in 1907, Stewart Edward White advises his reader to use only "OO canvas" for their canvas kayaks (not sure if they are letters or digits).
Does anybody know what kind of canvas it might have been back then? Does "OO" stands for a type/kind of canvas, or it was some manufacturer's brand name?
link to the publication below;
" The best sort are constructed of OO canvas." - https://www.google.com/books/edition/Camp_and_Trail/aE7TAAAAMAAJ?hl=en&gbpv=1&bsq=canvas - page 162

[Crossbar]

Just a guess but maybe it referred to the thickness of the canvas similar to how copper wire sizes are denoted in the U.S. '00' or 'Double Aught' being thicker than say #2 or #1.

[gpburdelljr]

Just a guess but maybe it referred to the thickness of the canvas similar to how copper wire sizes are denoted in the U.S. '00' or 'Double Aught' being thicker than say #2 or #1.
,
I believe you are correct. I did some web surfing and the heaviest canvas I could find was #4. The smaller the number, the heavier the canvas per yard. I couldn't find any 00, but presumably it is the heaviest canvas you could buy in the past.