Seeing the world through green-tinted glasses

Question

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 1828, a few decades before Baum was born, by Jane C. Loudon, in the second edition of 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.)

Answer 1

A possible common source for the idea of it being pleasant to look at things through emeralds is a passage in Pliny the Elder:

The third rank [of precious stones], for many reasons, has been given to the smaragdus. Indeed there is no stone, the colour of which is more delightful to the eye; for whereas the sight fixes itself with avidity upon the green grass and the foliage of the trees, we have all the more pleasure in looking upon the smaragdus, there being no green in existence of a more intense colour than this. And then, besides, of all the precious stones, this is the only one that feeds the sight without satiating it. Even when the vision has been fatigued with intently viewing other objects, it is refreshed by being turned upon this stone; and lapidaries know of nothing that is more gratefully soothing to the eyes, its soft green tints being wonderfully adapted for assuaging lassitude, when felt in those organs. […] In form they are mostly concave, so as to re-unite the rays of light and the powers of vision: and hence it is, that it is so universally agreed upon among mankind to respect these stones, and to forbid their surface to be engraved. In the case, however, of the stones of Scythia and Egypt, their hardness is such, that it would be quite impossible to penetrate them. When the surface of the smaragdus is flat, it reflects the image of objects in the same manner as a mirror. The Emperor Nero used to view the combats of the gladiators upon a smaragdus.

_{Pliny (79), Natural History 37.16, translated by John Bostock (1855).}

The meaning of this passage is not completely clear. Smaragdus seems to be a class of green precious stones that included emeralds, but likely also other kinds of stone, for most emeralds are too small to be used as mirrors. Fluorite, celadonite, dioptase, green obsidian, and other minerals have been suggested as possibilities.

As for “the Emperor Nero used to view the combats of the gladiators upon a smaragdus” (Nero princeps gladiatorum pugnas spectabat in smaragdo), in context a plausible reading is that he used the smaragdus as a concave mirror to increase the size of the image, since he was short-sighted:

Nero could see nothing distinctly without winking, and having it brought close to his eyes.

_{Pliny, Natural History 11.54.}

However:

An alternative reading of the text (smaragdo instead of in smaragdo) would suggest that Nero was using some kind of lens, but this possibility is not supported by the context of the evidence available.

_{Dimitris Plantzos (2013). ‘Crystals and Lenses in the Graeco-Roman World’, American Journal of Archaeology, 101:3, p. 462.}

This alternative reading led to the popular idea that Nero had looked at the games through an emerald, as a kind of precursor of sunglasses.