The great variety of tools represents the arts (measurement?), and the polyhedron and sphere are linked to geometry, the basis of all art. Talented people such as Durer saw themselves as melancholics, under the influence of the planet Saturn. The bat (is it a "bat"?) has been held to represent negative influences and the putto to represent industrious forces, and the hourglass, magic square, and scales to reflect divine creation. Is "creativity" the intersection of obsessiveness and self-doubt?
 
Engraving by Albrecht Durer, Nuremberg, 1514
Fine art replica print © 2006 by Allen Bjorkman