Damocles
3 of the 7 encyclopedias on this shelf carry an entry for Damocles. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a courtier of Dionysius, the tyrant of Syracuse. He lived in the first half of the fourth century before Christ. He had so much to say of the grandeur and happiness of kings, and was so given to flattery, that Dionysius prepared a surprise for him. Inviting him to sup, and placing him in a royal seat, he caused him to look upward in the very midst of the hilarity to behold a keen sword suspended above his head by a single hair. This quite altered Damocles' view of royal life, and gave him a sudden sense of the apprehension of danger under which rulers live. An allusion to the sword of Damocles is a well worn figure used to denote an impending danger that takes away the power of present enjoyment.
1000 Classical Characters (1900)
A Syracusan, one of the courtiers of Dionysius the elder. Damocles, having extolled the great felicity of Dionysius, was invited by him to a magnificent banquet, and was seated immediately below a naked sword which was suspended from the ceiling by a single horse-hair, a sight which explained to him at once what the felicity of a tyrant really was. The story is alluded to by Horace (C. iii. 1, 17).
Collier's New Encyclopedia (1921)
a sycophant at the court of Dionysius of Syracuse in the 4th century B. C. When he was one day extolling the happy condition of princes, the tyrant invited him to a sumptuous entertainment, but caused a naked sword to be suspended over his head by a single hair; a sufficiently significant symbol of the fear in which tyrants may live.