When you cover the egg with water, the water moves back through the membrane, rehydrating the egg. The next time you eat chicken, save some of the bones. Let a few of the bones dry out. Soak the rest of them in vinegar overnight. The next morning, remove the bones from the vinegar and try bending them.
Calcium carbonate makes bones stiff and hard.
Vinegar removes the calcium carbonate from the bones and makes them flexible.