These are Wilhelm M. Busch lithographs which are currently being offered on Ebay. The first two images are observations during Busch's life drawing classes. Boy, what would I give to have been one of his students way back. If any German reader had that experience, please leave us a comment on what that was like!
I do prefer this approach to drawing the human figure over the popular US style that is being taught in many art schools, which layers flashy shadows and highlights over the body like a special effect.
With Busch (as well as with Kley) the economy of the line rules.
Being a 2D animator my preference shouldn't surprise you.
This sketch had to be inspired by Heinrich Kley, because of the fantasy aspect.
A farmer on a wagon that's pulled by a donkey making his way through the the legs of a giant nude woman. I leave any sexual innuendo for you to interpret.