Detect a Changling

Changelings were fairy creatures that were left in the place of stolen children. The naughty fae folk often used to steal babies, and leave their own young in their place. If you suspected your baby had been replaced, this is what the mother of the child had to do:
Take 24 eggshells, set them up on the hearth, and start to brew beer. The changeling would then sit up and say:

"I heard it from my father, and he from his, and he from his, that an acorn was before the oak, and the oak was in the ground, but I have never seen brewing done in eggshells before!"

Which meant that it was definately a changeling.
Once you knew this the mother would heat a shovel until it was red-hot and hold the child above it and let it fall. The changeling would fly away up the chimney, laughing and shrieking, and the child would be returned safely.