 Powell links the horse to a woodcut by the German Renaissance artist Hans Baldung or to the marble "Horse Tamers" on Quirinal Hill, Rome.Fuseli may have added the horse as an afterthought, since a preliminary chalk sketch did not include it.Its presence in the painting has been viewed as a visual pun on the word "nightmare" and a self-conscious reference to folklore—the horse destabilises the painting's conceit and contributes to its Gothic tone.