Marcus Aurelius

Marcus Aurelius was a Roman emperor and a stoic philosopher.

Vastra claimed he was a bass player in a music band along with the Doctor too. (TV: Deep Breath)

Later references
Clara Oswald was a fan of the thinker and had a poster of his in her bedroom when she was 15. (TV: Deep Breath) She once taught a class at Coal Hill School in which she quoted him as saying, "Waste no more time arguing about what a good man should be. Be one." (TV: The Day of the Doctor)