Egg in grounds for percolated coffee. My aunt used to mix an egg into the grounds for making percolated coffee and it made the best coffee...Has anyone ever heard about it?

Egg shell has been used in brewing coffee for a very long time. The eggshells are mostly calcium and when dropped into coffee they will reduce the acidity of some coffees. Takes away the 'bite' in some coffees.

An old 'cowboy' trick.