According to the doctor of Louis XV, Monsieur de St André in his “lettres au sujet de la magie, sorcellerie et des sorciers” in 1725, it was believed that somebody displaying the following signs was convinced of being possessed by the Devil.

•  People being able to levitate without any exterior help or art
•  People being able to speak foreign or unknown languages (glossolalia) without any prior knowledge of them.  Inquisitors used to ask questions in foreign languages (german, latin,) and expected answers in the same language.  
• People being able to inform about events occuring in distant places or in the future.
• People being able to discover hidden things without any knowledge of them.
• People being able to guess thoughts and feelings that are not expressed to them

Other visible signs of possessions include contortions, unnatural body movements, insults, blasphemies, stigmata or wounds that vanish as quickly as they appear.