A sylph is an air spirit stemming from the 16th-century works of Paracelsus, who describes sylphs as (invisible) beings of the air, his elementals of air. A significant number of subsequent literary and occult works have been inspired by Paracelsus's concept: Robert Alfred Vaughan noted that "the wild but poetical fantasies" of Paracelsus had probably exercised a larger influence over his age and the subsequent one than is generally supposed, particularly on the Rosicrucians, but that through the 18th century they had become reduced to "machinery for the playwright" and "opera figurantes with wings of gauze and spangles".