"Mens Regum Bona Possidet," said Seneca, a Roman Philosopher of nineteen hundred years ago. Translated into English, this is what he said: "A good mind possesses a kingdom." A similar sentiment was expressed by Francis Quarles, an English poet of three hundred years ago: "My mind's my kingdom."
Marsh, Daniel L.
"Keys of the Kingdom of the Mind,"
Naval War College Review: Vol. 2
, Article 4.
Available at: https://digital-commons.usnwc.edu/nwc-review/vol2/iss8/4