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A Brief History of People Who Were Worried They Were Made of Glass

(Image credit: Flickr user Gilly Walker)

For more than 200 years, a peculiar delusion swept wealthier European households: People were convinced they were made of glass. The “glass delusion” remains a medical mystery, but it illustrates how the symptoms of mental illness change as new technologies appear.

French glassblowers develop “crown glass,” a new way of making windows. The wealthy eat it up. Lower-class windows remain made of cloth, parchment, animal hide, and even flattened animal horn.

King Charles VI of France dies after years spent convinced he is made of glass. Certain a wrong move would shatter him, Charles wore special clothes to avoid breaking into pieces.

The printing press sends literacy rates rocketing, leading to a boom in eyeglass production. Glass tableware and urinals also become more common among the well-to-do

Thomas Walkington writes of a Venetian man who’s also afraid of “crackling hinder-parts.” The delusion spreads and becomes literary fodder. In Thomas Tomkis’s play Lingua, the character Tactus says, “I am an urinal, I dare not stir for fear of cracking in the bottom.”

The delusion reaches new literary heights when Miguel de Cervantes Saavedra writes Doctor Glass-Case about a man “beseeching [people] not to come near him, or they would assuredly break him to pieces.”  

Alfonso Ponce de Santa Cruz aids a French prince who is so scared of cracking that he dares not leave his straw bed. (When that same bed somehow catches fire, it gets his glass in motion.)

In a letter, historian James Howell  gushes about Venice’s esteemed glass industry, saying it takes “a rare kind of knowledge and chymistry to transmute dust and sand.” He then insults a man who believes he’s a glass urinal.

A French glass-maker with the delusion wears a cushion on his derriere. He’s cured “by a severe thrashing from the doctor who told him that his pain emanated from buttocks of flesh,” Gill Speak writes in History of Psychiatry.

René Descartes mentions the delusion in his Meditations on First Philosophy, a treatise on God. (He also describes people who believe they are pumpkins.)

Glass loses its novelty, becoming cheap and common enough that even ordinary people can use it for windowpanes. The delusion begins to slide into obscurity.


The article above is reprinted with permission from the Scatterbrained section of the March-April 2015 issue of mental_floss magazine. Get a subscription to mental_floss and never miss an issue!

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