Writing backward was a favorite of Leonardo's and he was ambidextrous.

One of the interesting facts about Leonardo da Vinci is in his own writings, Leonardo always wrote from right to left. It is possible to read his writing from left to right if you hold a mirror up to the page. Leonardo wrote in this manner in part because he was left-handed and found it simpler to write from right to left.

According to several kinds of research, left-handed people tend to be more creative, and Leonardo most certainly fits that description. One of the most well-known painters who is known to have had a dominant left hand is the Renaissance man. With two hands, Leonardo da Vinci was able to draw simultaneously in both directions. In reality, he penned most of his learnings from right to left, creating a mirror script that was not the simplest to read.

It has been hypothesized that his backward writing was an effort to encrypt his words and thoughts to prevent them from being stolen. He did this to conceal his research since the concepts he was coming up with would have been condemned by the church in the fifteenth century (such as the use of dissections for anatomical studies). Another hypothesis is that because he wrote with his left hand, he wrote backward to prevent spreading the charcoal, chalk, or wet ink he was using. (Recent research has verified, however, what some have long suspected: Leonardo was ambidextrous and occasionally used his right hand for writing.)