French aviator and author Antoine de Saint-Exupéry's The Little Prince, published in 1943, has long been regarded as one of the most compelling books of the 20th century. Drawing upon Saint-Exupéry's own experiences in aviation, the book tells the tale of a pilot who crashes in the Sahara and befriends a little boy who claims to have come from outer space. The book is accompanied by a number of illustrations by Saint-Exupéry. Now, Smithsonian reports that some of the original preparatory sketches have surfaced.

According to France24.com, the sketches—of the titular Little Prince chatting with a fox, a boa constrictor devouring an elephant, and a character called the Tippler—were purchased at auction in 1986 by an art collector named Bruno Stefanini, who tucked them away in a folder. When Stefanini passed away in December 2018, the artwork—drawn on airmail paper—was uncovered by workers at his non-profit Foundation for Art, Culture, and History in Winterthur, Switzerland.

Aviator and The Little Prince author Antoine de Saint-Exupéry in 1935.Hulton Archive/Getty Images

The organization intends to share its findings with the Morgan Library and Museum in New York, which currently houses the original book manuscript (including drafts of the book's most famous phrase, "What is essential is invisible to the eye") and 35 other sketches.

The Stefanini collection also includes a particularly personal piece of material. One of the sketches includes a love letter made out to Saint-Exupéry's wife while the pilot was in New York in 1942 following Germany’s invasion of France. It was there he wrote The Little Prince, which was published the following year. In 1944, Saint-Exupéry was shot down by a German pilot over the Mediterranean.

[h/t Smithsonian]