Reflectivity

These days, we see ourselves all the time. Too much, in fact. From mirrors, to pictures, to zoom meetings, to shop windows, it is hard to go more than a few hours without seeing yourself reflected back at you. Being able to see yourself changes the way you interact with yourself and your world - from the way you dress to the way you feel at that important business meeting. People in the past may not have had high-quality mirrors or HD webcams, but they still looked at themselves, and it changed the way they saw the world, too. Any object that held liquid could become a mirror, capturing the world around it. It may not have been the primary (or even secondary) use of the object, but it was still an important material property of objects in the past.