|A sixteenth-century sign, posted in the Biblioteca de Salamanca in Spain, threatens excommunication to anyone stealing a book from the premises. seen here (PDF)
Hai excomunion reservada a su santidad contra qualesquiera personas, que quitaren, distraxeren, o de otro qualquier modo enagenaren algun libro, pergamino o papel de esta biblioteca, sin que puedan ser absueltas hasta que esta esté perfectamente reintegrada.
In English :
There is excommunication reserved to his holiness against any person who takes, loses, or other any way alienates any book, parchment or paper from this library, they can not be absolved until it is fully repaid.On 14 November 1568 Pope Pius V established a decree excommunicating book thieves leading to this sign. (almost related - Seinfeld s3e22 The Library)
The sign in context
What a marvelous looking library :