Leonardo the Enigma
weeklystandard.com
weeklystandard.com
He mentions it in The Cat Who Walks Through Walls if you are interested.
"In Robert Heinlen's The Door Into Summer, Dr. Twitchell recounts a tale of a student whom he displaced in time by 500 years. While there was no way of knowing whether the student went to the past or the future, Dr. Twitchell hints that he believes it was the past due to the student's name—Leonard Vincent."
https://en.wikipedia.org/wiki/Cultural_references_to_Leonard...