From the Witches Almanac my bible.

Black Box Invisibility Spell

Allegedly this spell enables you to maintain a low profile, especially when there is a threat of danger from another.

1. Make a figure representation of yourself (or the person desiring invisibility) from black clay (available from an art supply store).
2. Blend intimate items (hair, fingernail clippings, and similar) into the clay for maximum power.
3. Adorn the figure with black stones – anything other than black tourmaline. Obsidian is an excellent choice.
4. Cover with black feathers or wrap it in black velvet.
5. Place the figure within a small black box or a box made from mirrors or lined with mirrors. (If the box is large, place the figure in the center and surround it with black velvet.)
6. Place the box in a dark, quiet place.