The optical properties of crystal have always been known. In ancient Greece, scholars used crystal vessels filled with water to magnify letters and small stuff; in Imperial Rome, Nero famously used an emerald as a sort of natural telescope to better watch the gladiatorial games; in Arabia, mathematicians had been working on optical mirrors for ages. Everything changed however in 1100, in Venezia. The Venetian republic built the first glass industry in the world, keeping the secret of glassmaking well hidden by placing the factories on the guarded island of Murano. This allowed it both to experiment with various manufacturing techniques and to set extremely strict laws protecting the trade. It is by checking these laws that you can find specific norms relating to magnifying glasses and to eyeglasses’ lenses in the year 1284 – meaning that by that time the products were established and common enough that they had already been copied elsewhere. Historians thus place the birth of eyeglasses around the year 1180.
The first official and direct mention of actual eyeglasses comes however from a sermon delivered on the 23rd of February, 1306. In it, Friar Giordano da Pisa said that eyeglasses had been publicly on sale for little more than twenty years, but their manufacturing secret was withheld. It is believed that this inspired his colleague Alessandro della Spina to reverse-engineer a pair and finally reveal how they were bult a few years later. If these evidences weren’t enough, one could go for the first visual representation of glasses. It is a 1352 fresco in the Treviso priory of Saint Nicolò, showing forty preachers studying at their desk. One of them, Ugo da Provenza, is wearing what, without any doubt, is an early pair of hand-held glasses.