Leonardo da Vinci, the quintessential Renaissance Man, was famous for his habit of 'mirror writing.' Most of his personal notebooks were written from right to left, meaning they could only be read easily when held up to a mirror. While some historians suggest he did this to keep his ideas secret from prying eyes or the Church, a more practical explanation is that Leonardo was left-handed. In the 15th century, writing with a quill pen from left to right would cause a left-handed person to smudge the wet ink with their hand. By writing in reverse, he avoided this mess. His notebooks, such as the Codex Leicester, contain thousands of pages of scientific observations, anatomical drawings, and engineering designs that were centuries ahead of their time, all rendered in this distinctive script.