Wikipedia Entry for the Night

Glass delusion:

The glass delusion was an external manifestation of a psychiatric disorder recorded in Europe in the late middle ages (15th to 17th centuries). People feared that they were made of glass “and therefore likely to shatter into pieces”. One famous early sufferer was King Charles VI of France who refused to allow people to touch him, and wore reinforced clothing to protect himself from accidental “shattering”.

(via Best of Wikipedia)