space.
It was documented as early as 1770 and spread widely after its use by the charlatan Johann George Schropfer,
who claimed the apparitions to be conjurered spirits.
It subsequently became a fixture of 19th-century phantasmagoria shows.
The illusion relies on a hidden projector (known then as a magic lanern) the beam of which reflects off a mirror
into a cloud of smoke, which in turn scatters the beam to create an image.
The phrase "smoke and mirrors" has entered common English use to refer ro any proposal that, when examined
closely, proves to be an illusion.