Edward Weston's Day Books, entry dated 3/6/29
"My best work is more analogous to architecture and sculpture than to painting. I made a posterior view, in flat, but very brilliant light, which outlines the figure with such a definite black line, that even photographers swear I have pencilled the negative,--I have used this light before on the dancing nudes."
Also, in the daybooks, Weston mentioned that he never uses artificial light...only natural light.
I believe this outline can also be seen lightly in the Charis nudes in the dunes.
As a side point...I have the Knees print in (at least) two books and noticed that they each are a different crop and contrast. I guess book prints always have to be taken with a grain of salt.
I vaguely remember reading more on this outline effect but know not where.
Hope this helps,