The Voynich Manuscript

https://archive.org/details/TheVoynichManuscript

''The Voynich manuscript is an illustrated codex hand-written in an unknown writing system. The vellum in the book pages has been carbon dated to the early 15th century (1404–1438). The mystery of the meaning and origin of the manuscript has excited the popular imagination, making the manuscript the subject of novels and speculation. None of the many hypotheses proposed over the last hundred years has yet been independently verified.''

https://en.wikipedia.org/wiki/Voynich_manuscript