Scrying can be defined as the mantic art of gazing into or upon a crystal or dark mirror. The black scrying mirror is a powerful psychic tool, it allows communication with higher realms and the subconscious.
Practised by John Dee & Edward Kelley. From the English word descry, meaning to reveal, scrying is the art of clairvoyance achieved by concentrating on an object, usually one with a reflective or semi-reflective surface (typically a mirror, a crystal ball or water) until visions appear. Dee used a black mirror made of obsidian which he called a 'shewstone' because it 'shewed' (showed) the future.