This is the earliest known eyewear, dating back to the Roman Emperor Nero’s reign (54 to 68 A.D.). It was said that the emperor watched the gladiatorial games using these lenses. Whether or not they are set in frames is unknown. Additionally, Seneca the Younger, one of Nero’s tutors, wrote on how to magnify letters using a water-filled sphere or glass. This invention was possibly used by the emperor as well.