One of them has to be replaceable underwear. BEfore the advent of high-speed automated weaving, underwear only got changed when you peeled it off to wash it and then put it back on again. Let's hear it for fruit of the loom! A major contributor to public health.

I am personally fond of the thermos bottle. When you put something hot in it, it keeps it hot. If you put something cold in it, it keeps it cold. So HOW does it KNOW???