Two drawings from casts sale on Ebay. The drawing of plaster casts on figures was the accepted method to beginto learn to draw the figure in 19th century art schools. The Figure on the left is Dionysus. on the right Apollo. Compare the drawings with an orignal Dionysus in the Louvre, and compare the Apollo with the drawing Apollon dit L'Adonis by Chatillon and the engraving of the statue from the Louvre by Henri-Guillaume Chatillon fom the book written by Duchesne Aine from Musée Francais; Recueil Des Plus Beaux Tableaux, Statues, et Bas-Reliefs Qui Existaient Au Louvre Avant 1815. The images of Apollo are from the George Glazer Gallery.
How to Draw - Drawing from Casts, Academic Drawings - The Ecole Des Beaux-Arts, Paris - Drawing from Life, Prints from Jean Duchesne Aine’s Musee Francais.
Model Drawing and Shading From Casts: A Complete Guide to the Elementary and Advanced Examinations in These Subjects 
An Elementary Course in Free Hand Geometrical Drawing