La extracción de la piedra de la locura

Around 1500 there was a grim joke that a madman had a stone lodged in his skull, and that a clever operator could cut it out and cure him. Bosch paints exactly that scene and lets you see the con. A patient sits tied to a chair while a surgeon opens his head, and what comes out is not a stone but a flower bulb, with another bloom already on the table. The surgeon wears an upturned funnel on his head, which to viewers then marked him plainly as a charlatan. Gold letters loop around the scene in old Dutch. No stone was ever there, and everyone in the picture seems in on it except the man in the chair.