Before glass was introduced in 1300 A.D., manufactured mirrors were simply polished metal.
Around 6 B.C., in much the same manner one would now use as a crystal ball, the Greeks began practicing fortune-telling from a subject’s reflected image in a bowl of water.
If, during a reading, the bowl with the image fell and broke it meant disaster.
The Romans limited the curse to seven years because they believed that’s how long it took for human life to renew itself.