Is the glass half-empty, half-full, or COMPLETELY empty?

Recently I visited an Italian restaurant that served water in tall glasses. At the end of my meal, it appeared that I had some more water left in my glass. I was still thirsty so I decided to finish it off. When I picked up the glass, I realized that there was actually no water in it at all -- just an illusion created by a ridge on the inside. It just struck me funny as I was thinking, “Hmm… this gives new meaning to that old phrase…”