From Grimorium Verum, Plangiere edition:
To make yourself go invisible
Collect seven black beans. Start the rite on a Wednesday, before sunrise. Then take the head of a dead man, and put one of the black beans in his mouth, two in his eyes and two in his ears.
Then make upon his head the character of Morail.
When you have done this, bury the head, with the face upwards, and for nine days, before sunrise, water it each morning with excellent brandy. On the eighth day you will find the spirit mentioned, who will say to you: "What wilt thou?"
You will reply: "I am watering my plant." Then the spirit will say: "Give me the bottle, I desire to water it myself." In answer, refuse him this, even though he will ask you again.
Then he will reach out with his hand, and will display to you that same figure which you have drawn upon the head. Now you can be sure that it is the right spirit, the spirit of the head.
There is a danger that another one might try to trick you, which would have evil consequences—and in that case your operation would not succeed.
Then you may give him the bottle, and he will water the head and leave. On the next day--which is the ninth--when you return, you will find the beans that are germinating. Take them and put them in your mouth, and look at yourself in the mirror. If you can see nothing, it is well. Test the others in the same way, either in your own mouth, or in that of a child.
Those which do not confer invisibility are to be reburied with the head.
From Hygromanteia, Ioannis Marathakis edition:
Take the dry skull of a man that did not die a natural death. Go to a secret, inaccessible and impassable place and recite these names over the skull.
Grant invisibility, Lord, in the names Theophael, Diokaides, Peridon, Enarkale, Esboiel, Apelout, Gakarkentos, so that this work will be effective.
Then, take seeds of the herb korakia. The Romans call it phabenbesia, that is to say broad bean. Plant one seed in each of the eyes, and put another one in the mouth. Cover with earth and recite the following.
As the eyes of the dead do not see the living, so these beans may have the power of invisibility, wherever I may go.
And when the beans yield seed, be careful not to lose any of them, but take them out and keep them all together. Then, bring a mirror and take each bean in your hand, one by one. If you do not see yourself in the mirror, this particular bean has power. Carry it upon you and go wherever you wish. Nobody will see you.