The Battle of Anghiari, commissioned in 1503, was never finished. The cartoon — the preparatory drawing — was considered by many contemporaries the greatest drawing ever made. It is lost.

Above all, Leonardo's relentless curiosity and experimentation should remind us of the importance of instilling, in both ourselves and our children, not just received knowledge but a willingness to question it — to be imaginative and, like talented misfits and rebels in any era, to think different.