This section is from the book "Ancient Legends, Mystic Charms, And Superstitions Of Ireland", by Jane Francesca Wilde. Also available from Amazon: Ancient Legends, Mystic Charms, And Superstitions Of Ireland.
Get a raven's heart, split it open with a black-hafted knife ; make three cuts and place a black bean in each cut. Then plant it, and when the beans sprout put one in your mouth, and say-
" By virtue of Satan's heart, And by strength of my great art, I desire to be invisible."
And so it will be as long as the bean is kept in the mouth.