Rinse the eggs clean and clean them. Carefully place in a tall container with the shell to save space. Squeeze the lemons well. Pour enough juice over the eggs to cover them. Leave for 8 to 10 days, stirring in between, until the eggshells are loosened.
Now put everything together in a sieve, better through a muslin cloth and drain. Stir the egg-lemon mixture with the rum and sugar until the sugar is completely dissolved and a homogeneous cream is formed. With the back of a knife, scrape the vanilla pulp from the pods and also mix well into the creamy mixture.
Add a little sugar if you like. Close the resulting eggnog well and keep it cooled.
This old home elixir, which used to alleviate many an ailment, is still helpful today. It gives strength and protects against colds.