Male Nude Leaning on a Ladder

The reason I really like this drawing is that it is the perfect thing to copy if you'd like to really challenge and push your skills. And the specific reason for that is in this drawing you can see clearly most of the individual lines and strokes of charcoal that the artist used to model the human form. 

If you look at the drawing I've posted by Prud'hon, its charm comes from the subtlety of the modeling of the form. The modeling is created with charcoal, white chalk, and using a stump to create the soft transitions. 

There is an easy trap to fall into when trying to create a realistic drawings in this mode of black-charcoal, white-chalk, and stump. The trap is to think that most of the modeling should be done with the stump. Actually, most of the modeling should be done with careful hatching with charcoal. The stump and white chalk should only be used at the end to gently pull everything together. 

This drawing by Batoni has minimal stump work and blending, which allow us to see clearly the exact lines he used with charcoal to model the figure.