Leonardo’s mirror writing was ordinary to him

Many of Leonardo da Vinci’s surviving notes run from right to left and are easiest to read in a mirror. Because the pages also contain machines, anatomy and private thoughts, the habit is often presented as encryption. Yet Leonardo was left-handed, and reverse writing may simply have made pulling a quill across the page more comfortable and reduced smudging.

No document gives one final reason, and he could write conventionally when a recipient required it. The useful surprise is not that a genius hid every idea in code. It is that a working notebook may preserve the bodily convenience of its maker. A page can look mysterious to later viewers while functioning as an everyday tool in the hand that made it.