Cesare Ripa’s Iconologia, first published in 1593, was an encyclopedia of allegorical imagery which was used by artists in order to a learn how to represent abstract ideas in personified form, that is, in the form of human figures with attributes that would enable viewers to identify them and contemplate their significance. Art historians frequently turn to it in their efforts to interpret old pictures; Peter was prompted to create his own series of illustrations. Ripa describes Imagination as a richly-dressed woman with wings at the side of her head and a crown of dancing figures. He explains that the figures represent the turbulent abundance of the imaginative mind. Meller follows Ripa closely but makes one change: where the author would have Imagination looking heavenward, Peter shows her with her eyes closed, as if in deep, rapturous contemplation of her many ideas.