Scientists have confirmed that a copy of Des destinees de l’ame (Destinies of the Soul) owned by Harvard University’s Houghton Library is, as has long been rumored, bound in human skin, reports the BBC.

The book was donated to the school in 1934. Allegedly the author, Arsène Houssaye, gave the book to his friend, Ludovic Bouland, in the mid-1880s. Bouland embellished the book with a special binding, made from skin taken from the body of an unclaimed female mental patient—and even though she died of natural causes, it’s still quite disturbing.

What could have inspired Bouland to do such a thing? “I had kept this piece of human skin taken from the back of a woman,” he wrote on an inscription inside the tome. “A book about the human soul deserved to have a human covering.” He didn’t mark the cover with a title or author, because he wanted to “preserve its elegance”.

Even more shocking, the Harvard library alone had two other candidates for the dubious distinction of being a rare example of anthropodermic bibliopegy, or books bound in human flesh. According to the New York Times, both the other editions were found to be sourced from comparatively more pedestrian sheepskin in April.

The methods used to test the book binding included a protein-identifying technique called peptide mass fingerprinting (PMF) and liquid chromatography-tandem mass spectrometry to analyze amino acid order.

“The PMF from Des destinées de l’ame matched the human reference, and clearly eliminated other common parchment sources, such as sheep, cattle, and goat,” said Bill Lane, the director of the Harvard Mass Spectrometry and Proteomics Resource Laboratory, and Daniel Kirby, of the Straus Center for Conservation and Technical Studies, in an interview with the Houghton Library Blog.

While it is still theoretically possible that the cover could be made of great ape and gibbon, it seems unlikely based on the book’s provenance.

A book bound in human skin may seem unthinkably grotesque today, but the practice appears to date back to the 16th century. During the 19th century, when the corpses of executed criminals were donated to scientists, their skins would often make their way to bookbinders. Family members might also use the practice as a means of memorializing a dead loved one.

Books aren’t the only objects that have purportedly utilized human skin in unexpectedly macabre ways. Many believe that Ilse Koch, the wife of a Nazi commandant, collected lampshades made from skin harvested from Jews killed at the Buchenwald concentration camp.

In 2010, New York magazine published an excerpt from Mark Jacobson’s The Lampshade: A Holocaust Detective Story from Buchenwald to New Orleans. After Hurricane Katrina, a mysterious lamp surfaced in New Orleans along with unconfirmed rumors that it bore one of the legendary Buchenwald lampshades. Scientific tests conducted in 2012 ruled conclusively that the lamp was made from cow skin.