In 1842, he stole the Ashburnham Pentateuch at the Library of Tours. Thanks to the blind confidence of the canon Hyacinthe Olivier-Vitalis, he seized at the Inguimbertine library of Carpentras numerous documents such as the " Works of Théocrite and Hésiode " (Venice, Alde, 1495) or 72 of 75 letters of Descartes to Father Mersenne (between 1837 and 1847). He did not, occasionally, hesitate to mutilate certain manuscripts: five volumes of the Peiresc fund and at least two thousand leaves so disappeared. In 1848, as France was involved in a liberal revolution and the government fell, a warrant was issued for Libri's arrest.