The mysterious Voynich manuscript at the Beinecke Rare Book & Manuscript Library. You can look at it page by page on this website.
Excerpt from the website:
Written in Central Europe at the end of the 15th or during the 16th century, the origin, language, and date of the Voynich Manuscript—named after the Polish-American antiquarian bookseller, Wilfrid M. Voynich, who acquired it in 1912—are still being debated as vigorously as its puzzling drawings and undeciphered text. Described as a magical or scientific text, nearly every page contains botanical, figurative, and scientific drawings of a provincial but lively character, drawn in ink with vibrant washes in various shades of green, brown, yellow, blue, and red.