"speak with those they call angels and demons through just such showing-stones, or else a speculum made for the purpose"

The Crystal Ball
Public DomainThe Crystal Ball - Credit: John William Waterhouse
Showing-stones or crystal balls were balls of glass or crystal that were believed to aid in clairvoyance, magic, and communicating with spirits. A speculum was a table showing the relative positions of the planets, used in astrology.