“Cochemare” [trans. “the night-mare”] (1810) engraving by Jean Pierre Simon. Source: Wellcome Library.

That object – no larger than a good-sized rat and quaintly called by the townspeople “Brown Jenkins — seemed to have been the fruit of a remarkable case of sympathetic herd-delusion, for in 1692 no less than eleven persons had testified to glimpsing it. There were recent rumours, too, with a baffling and disconcerting amount of agreement. Witnesses said it had long hair and the shape of a rat, but that its sharp-toothed, bearded face was evilly human while its paws were like tiny human hands. It took messages betwixt old Keziah and the devil, and was nursed on the witch’s blood, which it sucked like a vampire. Its voice was a kind of loathsome titter, and it could speak all languages. Of all the bizarre monstrosities in Gilman’s dreams, nothing filled him with greater panic and nausea than this blasphemous and diminutive hybrid, whose image flitted across his vision in a form a thousandfold more hateful than anything his waking mind had deduced from the ancient records and the modern whispers.” — H.P. Lovecraft, “Dreams in the Witch House” (1932).

Simon was undoubtedly inspired by the famous “The Nightmare” (1781) by Johann Heinrich Fussli…

Lovecraft was probably also inspired by this widely known work by Fussli (later known as Henry Fuseli), whom he knew of and admired…

I don’t have to tell you why a Fuseli really brings a shiver while a cheap ghost-story frontispiece merely makes us laugh.” — “Pickman’s Model” (1926).

From Lovecraft’s Commonplace Book of story ideas, #106…

A thing that sat on a sleeper’s chest. Gone in morning, but something left behind.”

I also found this rather cool “Hypnose” (1904) by Sascha Schneider.

The uses of the light-shaft, the opium poppies, and the older/younger man pairing all signify the artist’s knowledge of the details of the Hypnos myth, something Lovecraft also used…

a shaft of horrible red-gold light — a shaft which bore with it no glow to disperse the darkness, but which streamed only upon the recumbent head of the troubled sleeper […] “I followed the memory-face’s mad stare along that cursed shaft of light to its source” — H.P. Lovecraft, “Hypnos” (1922).

Schneider was a contributor to Brand’s pioneering gay publication Der Eigene and also illustrator of Old Shatterhand / Winnetoue, the very Teutonic wild western series that was a best-seller in early 20th century Germany and probably also among German immigrants to America. It turns out that finding Schneider’s “Hypnose” led me back to his various broad variations on Fussli’s “The Nightmare”…

Above: all untitled except the last two, a Karl May book illustration, and “Around a Soul”.

There is an English language masters dissertation on Schneider which is available online: Monsters and Men: The Life and Works of Sascha Schneider.

It seems there were also fictional depictions of this chest-squatter, one of which was noted by Lovecraft in Fitz-James O’Brien’s story “What Was it? A Mystery” as a predecessor of de Maupassant’s “The Horla”.

For a full book on the history of the topic see Sleep Paralysis: Night-Mares, Nocebos, and the Mind-Body Connection (Studies in Medical Anthropology) (2011).