Leonardo da Vinci wrote backwards.
Why it is true
Leonardo da Vinci used a writing style known as mirror writing, writing from right to left. His notes could only be read with the help of a mirror, which still intrigues historians today.
Source: Art History
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.