A typical sufferer might have believed he was "a urinal, an oil lamp or other glass receptacle, or else they might themselves trapped within a glass bottle."
A 1561 medical account describes a patient "who had to relieve himself standing up, fearing that if he sat down his buttocks would shatter... The man concerned was a glass-maker from the Parisian suburb of Saint Germain, who constantly applied a small cushion to his buttocks, even when standing. He was cured of this obsession by a severe thrashing from Doctor Chris Lorch, who told him that his pain emanated from buttocks of flesh."
Concentration of the glass delusion among the wealthy and educated classes allowed modern scholars to associate it with a wider and better described disorder of scholar's melancholy.
Robert Burton’s The Anatomy of Melancholy (1621) touches on the subject in the commentary as one of many related manifestations of the same anxiety: “Fear of devils, death, that they shall be so sick, of some such or such disease, ready to tremble at every object, they shall die themselves forthwith, or that some of their dear friends or near allies are certainly dead; imminent danger, loss, disgrace still torment others, & that they are all glass, and therefore will suffer no man to come near them; that they are all cork, as light as feathers; others as heavy as lead; some are afraid their heads will fall off their shoulders, that they have frogs in their bellies, Etc.".
French philosopher René Descartes wrote Meditations on First Philosophy (1641), using the glass delusion as an example of an insane person whose perceived knowledge of the world differs from the majority.
In modern times, the glass delusion has disappeared. “Surveys of modern psychiatric institutions have only revealed two specific (uncorroborated) cases of the glass delusion. Foulché-Delbosc reports finding one Glass Man in a Paris asylum, and a woman who thought she was a potsherd was recorded at an asylum in Merenberg.”