The Fairy Feller's Master Stroke

By Richard Dadd, painted 1855-1864. At the Tate Gallery, London.
From www.tate.org.uk/:

Dadd painted this work in the Bethlem Hospital where he was sent after murdering his father and being declared insane. The scene was drawn from his imagination. It shows the ‘fairy-feller’ poised to split a large chestnut which will be used to construct Queen Mab’s new fairy carriage. The subject, shifting scale and style of the painting all contribute to a sense of the fantastic that fits Herbert Read’s idea of an imaginative tradition that runs through to Surrealism. The work might also have fitted the Surrealists’ interest in the art of the insane.

From wikipedia:

The Fairy Feller's Master-Stroke is a Richard Dadd painting. It was commissioned by George Henry Hayden, who was head steward at Bethlem Royal Hospital at the time. He was impressed by Dadd's artistic efforts and asked for a fairy painting of his own. Dadd worked on the painting for nine years - paying microscopic attention to detail, as well as a layering technique producing near-3D results - and it is generally regarded as his most important work. However, Dadd himself considered the painting to be unfinished, and as such added the suffix of "Quasi" to its title.