Cinderella’s Glass Slipper has become so much part of the fairy tale that to change it in any way would spoil its charm. After all, it was by means of the glass slipper dropped by Cinderella on leaving the ball that the prince who had fallen in love with her, was able to find her again.
However, with a little thought, it becomes apparent that glass slippers fit neither into the story nor on Cinderella’s feet! No one would wear them on a cold winter’s night. Moreover, to dance in them would prove very difficult.
And, in fact, the earliest French version of the tale does not speak of glass slippers, but slippers made off fur, much more in charaster with the story, the season and the occasion. Comfortable to dance in, fur slippers would keep Cinderella’s feet warm in the coldest of nights. They would have been of white ermine, fit for a princess!
The French for “fur” is vair and for "glass", verre. Differently spelled, the two words are almost identical in sound. It was quite easy to mistake one for the other. (It must be remembered that, at the time, stories were mostly not read from a book, but related by word of mouth) Not magic therefore, but an error changed the fur into glass!
For once the perpetrator of the mistake can be identified. It was the french poet and critic(!) Charles Perrault who in 1697 published the story in a collection of popular fairy tales. He selected it from several versions of ‘Cinderella’ then in circulation and at his disposal. Each one spoke of a fur slipper which he – erroneously-turned into glass. As all later editions and translations of the fairy tale were based on his text, they coppied his mistake, which never been corrected.

( Souces: Mistakes, misnomers and misconceptions – R Brusch 1983)