Percy Bysshe Shelley
Percy Bysshe Shelley was an Earth poet. He wrote, "All spirits are enslaved that serve things evil." He was also the husband of Mary Shelley. (ENT: "Horizon")
In 2364, Captain Jean-Luc Picard quoted this line in a conversation with Armus. Picard's point was that to do the bidding of Armus would enslave the crew of the USS Enterprise-D. Armus took the quote literally and argued that he wasn't a servant of evil, he was evil itself. (TNG: "Skin Of Evil")
The poet is not referred to by name in the episode other than as "a great poet." Picard quotes from the poem Prometheus Bound, line 110.