A Treatise on Painting/Chapter 21

Chap. XXI.Of studying in the Dark, on first waking in the Morning, and before going to sleep.

I have experienced no small benefit, when in the dark and in bed, by retracing in my mind the outlines of those forms which I had previously studied, particularly such as had appeared the most difficult to comprehend and retain; by this method they will be confirmed and treasured up in the memory.