show-stone

The learned professor thought that witchcraft might be proved by witnesses who have heard the accused person invoking the devil for help, or seen the suspected party entertaining a familiar spirit and feeding it in any form or likeness, conjuring to raise storms, showing in a glass or show-stone the faces of absent persons.

The Mysteries of All Nations Rise and Progress of Superstition, Laws Against and Trials of Witches, Ancient and Modern Delusions Together With Strange Customs, Fables, and Tales James Grant

His show-stone or mirror is still preserved among other curiosities in the British Museum.

Letters on Demonology and Witchcraft 1885

His show-stone or mirror is still preserved among other curiosities in the British Museum.

Letters on Demonology and Witchcraft Walter Scott 1801