I find the history of mirrors kind of fascinating (nerd alert), but especially because it does have an impact on certain fairy tales and how we look at them-most notably Snow White.
It's hard for me to wrap my mind around it, but for the majority of human history, a decent mirror has been a luxury that only a few had access to. Most early mirrors were made of polished metal, so even the best ones would have dark, uneven reflections. The first glass mirrors were still "always slightly curved, and always slightly colored." Once the Venetians started mastering glass mirrors, they became an incredibly valuable commodity. The trade secrets were worth kidnapping for, as eventually happened when the French decided they needed to manufacture the luxury themselves (and as a rule, Italian mirror makers' families would be held hostage whenever they traveled, to insure loyalty).
Even when mirrors became more broadly produced, they were incredibly expensive. Most cultured ladies would have a pocket mirror that was very valuable-there is an anecdote of one lady trading a wheat field for a mirror. It was only the extreme indulgence of Louis XIV that pushed mirror makers to discover a way to make mirrors larger, and thus create the famed Hall of Mirrors.
The majority of humans in history would have only seen reflections of themselves in smooth surfaces, such as water. It's no surprise that in many versions of Snow White, the evil Queen does not ask a mirror to proclaim the fairest of them all, but other objects of nature, such as the sun or moon, or even an animal such as an eagle or trout. It makes more sense to imagine a woman, in a world in which you could never really see what you look like, to wonder how you compare to the other beautiful women you see, and ask someone else for their opinion. The sun, moon, or eagle would have authority to make a pretty good judgment, for they would see a great number of people as they made their way across the sky (not sure about the trout, but that's not as common).
A. W. Bayes, "The Snow Queen"
Mirrors have great capacity for new boundaries in art, science, and self-reflection. Yet mirrors also have dangers, ones that we tend to take for granted, especially now that we see images of ourselves more often than ever on social media and the ubiquitous selfie. In a way, we are all now the Queen, whenever we look at a picture of ourselves and contrast our looks with others (and if we're honest, don't we all do it?). In an incredibly visually oriented world that promotes conventional beauty as the ideal, it becomes more and more difficult to avoid assigning value by physical appearance.
The History of a Mirror: Through a Glass Darkly by Stephanie Lowder
The Essence of Style by Joan deJean
Sleeping Beauty and Snow White Tales from Around the World by Surlalune
Illustrations: P.J. Lynch, John Patience, Hans Juttner, A. W. Bayes, H.J. Ford