Samizdat

“A Kraków codex of encyclopedic content and of necromantic fame, the Liber viginti artium (Book of the Twenty Arts) of Paul of Prague, was believed to bear the traces of the touch of the devil.

Its demonic power was so feared even in the eighteenth century that the book was hidden under a stone for some years so that it could not be read; other reports claim that it was chained to the wall in the library of Vilnius. From time to time, the book is believed to possess sinister powers as if malign demons might reside in it. Various descriptions have come to us reporting that when such books were burned, bystanders heard the voices of escaping demons.

[…]

However, we do not necessarily need to hear escaping demons to view magic codices with a certain interest (or suspicion). As the main vehicles of secret and forbidden knowledge, they are responsible for the dissemination of learned magic, and their destruction or survival greatly depends on the picture they construct. Sometimes their attempt at legitimating their magical content by creating a most holy image remains unsuccessful and leads to the formation of an opposite, diabolical impression. We will see this (at least partly) failed effort in the case of the Ars notoria and the Liber visionum, the latter of which was not only condemned but also burned in Paris.

Benedek Láng, Unlocked Books: Manuscripts of Learned Magic in the Medieval Libraries of Central Europe, 2008: pg. 48.