people thus situated, who have warm imaginations, generally amuse themselves by conjuring up an idol of perfection to which they attach all kinds of merit, probable or improbable. They invest the first face or figure that takes their fancy, with these imagined charms, no matter whether they accord or not, and then fall in love with the image they have created—whilst the delusion under which they labour, makes them see every action of the beloved object under a false light; just as people wearing green spectacles fancy the whole creation tinged with emerald.
This is, of course, an obvious allusion to the Emerald City in The Wonderful Wizard of Oz by L. Frank Baum. Except that it was written in 1827, a few decades before Baum was born, by Jane C. Loudon, in The Mummy!: Or a Tale of the Twenty-Second Century (available online).
It could be a coincidence, but I wonder. Have other authors suggested people with red glasses seeing a world made or rubies, and people with yellow glasses seeing a world made of citrine? Or was Frank making a reference to Loudon? Or were they both part of a larger movement, and if so is it purely an arbitrary tradition or is it based on some symbolism of emeralds?
How does the literary history of green spectacles match that of rose-colored glasses?
(Note that I'm asking why emeralds and not other gems. The association between emeralds and green, and the symbolism of gems as precious and nice-looking, are obvious.)