This morning I ran across a nice series of 19th century academic drawings from an unknown European atelier which demonstrates beautifully the 19th century atelier teaching method of "blocking in," drawing from a master drawing, and drawing from the plaster cast. I think Juliette Aristides describes the process best in chapter one of her book... Classical Drawing Atelier:
"The heart of atelier curriculum is drawing from life and working on individual tailored independent projects. ...... The first year of study also focuses on executing master copies and cast drawings using charcoal or graphite on paper. A master copy is a replica of a noteworthy work of art by a master artist. A cast drawing, or a drawing from a replica of a classical sculpture could be considered a master copy in which students begin to learn how to translate the three dimensions seen by the eye into the two dimensions available on paper or canvas. Both of these exercises offer students a chance to work on an extended drawing without the inherent difficulties of drawing from life, such as the model moving or the pose ending before the completion of the drawing. Both exercises are solitary experiences that require an enormous investment of time and provide a glimpse into what it is like to be an artist in a studio. Students spend at least the first year of their training drawing from life and creating master copies and cast drawing before moving on to painting."
(pg. 10 - 11, chapter one, Classical Drawing Atelier, by Juliette Aristides, ISBN: 978-0-8230-0657-1)