Lexitechnia

Pliny on mirrors (Naturalis Historia 33.45):

Plurimum refert concava sint et poculi modo an parmae Threcidicae, media depressa an elata, transversa an obliqua, supina an recta, qualitate excipientis figurae torquente venientes umbras.

It matters greatly whether they are concave like a cup or like the Threx’s parma shield, whether they are lowered or raised in the middle, straight across or at an angle, whether horizontal or upright, the quality of the receiving shape reflecting the incoming shade.

Normal mirrors don’t try to distort the reflection, but Pliny is talking about what we might call funhouse mirrors, here called [specula] monstrifica (lit. ‘monstrous mirrors’), though his example is not in a funhouse but the temple of Smyrna.

This line includes several contrasting pairs. About half the versions of this text say supina an recta (‘on its back or upright’); the others generally say supina an infesta, which I couldn’t really make sense of; dictionary senses of infestus are ‘unsafe’ and ‘aggressive’, neither of which readily applies to the shape of a mirror.

The cultural reference parma Threcidica is difficult to relate cleanly in the translation; the Threx (or thraex, as wikipedia spells it) was a kind of gladiator who was armed in a Thracian style; the parma was the shield they used. In the translation I decided to support parma with a gloss and let the proper noun Threx stand for itself.

As for umbra ‘shadow’, it does seem that, unlike the modern idea that mirrors reflect light of surfaces themselves not emitting light, Pliny saw the reverse; he goes on to say neque enim est aliud illa imago quam digesta claritate materiae accipientis umbra (‘for neither is the reflection anything other than shadow arranged in the brightness of the receiving material’).

[For qualitas.]