From The Black Books of Elverum, Mary S. Rustad edition:
To make yourself invisible
Poke out the eyes of a bat and put them in your pocket. Smear yourself with bat's blood. Then take the eye of a black cat. Cook it in sweet milk. After eating and drinking this, you'll be invisible for nine hours.
This spell is similar to the spells To make oneself invisible To make yourself invisible
The grimoire The Black Books of Elverum lists this spell.