Guglielmo Libri Carucci Dalla Sommaja

Guglielmo Libri Carucci dalla Sommaja (born January 1, 1803 in Florence, Italy; died September 28, 1869, in Fiesole, Italy) was an Italian count and mathematician, who became known for his love and subsequent theft of ancient and precious manuscripts.

Appointed the Inspector of Libraries in France, Libri began stealing the books he was responsible for, fleeing to England when caught, along with 30,000 books and manuscripts inside 18 trunks. He was sentenced in France to 10 years in jail in absentia; some of the stolen works were returned when he died, but many remained missing.

In June 2010, one of the documents he stole—a letter from the French philosopher René Descartes, dated May 27, 1641—was handed back to France after being found in a library in Haverford College, in Pennsylvania. The letter had been donated by the widow of a college alumnus in 1902, and was discovered only after a philosopher from Utrecht University in the Netherlands read about it on the Internet, and contacted the college to tell them what they had in their library; the existence of the letter had been known to philosophers, but not its contents. The letter was written by Descartes to Father Marin Mersenne who had been overseeing the publication of Descartes's Meditations on First Philosophy.