The origin of these valuable instruments is uncertain: that the ancients
were acquainted with the laws of refraction is beyond all doubt, since
they made use of glass globes filled with water to produce combustion; and
in Seneca we find the following very curious passage--"Litterae, quamvis
minutiae et obscurae, per vitream pilam aqua plenam majores clarioresque
cernuntur;" yet thirteen centuries elapsed ere spectacles were known. It
is supposed that they were first invented by _Salvino_ or _Salvinio
Armati_; but he kept his discovery secret, until Alessandro de Spina, a
monk in Pisa, brought them into use in 1313. Salvino was considered their
inventor, from the epitaph on his tomb in the cathedral church in
Florence: "Qui giace Salvino d'Armato, degl' Armati di Firenze, inventor
delli occhiali, &c., 1317." Another circumstance seems to add weight to
this presumption: _Luigi Sigoli_, a contemporary artist, in a painting of
the Circumcision, represents the high-priest Simeon with a pair of
spectacles, which, from his advanced age, it was supposed he might have
needed on the occasion.