TIL the 16th century philosopher Michel de Montaigne was raised in an experiment by his parents to learn Latin as a first language. From birth, his tutor, servants and parents were only ever allowed to speak to him in Latin.

https://wikipedia.org/wiki/Michel_de_Montaigne

https://www.reddit.com/r/todayilearned/comments/15jj5xs/til_the_16th_century_philosopher_michel_de/