Forget the theory of relativity. When it comes to decoding the universe, nothing is more mysterious than human beings. Thankfully, German-born physicist and world-famous genius Albert Einstein has left behind his own theory to achieving happiness and fulfillment—and no, it has nothing to do with physics.

After 95 years, an anonymous seller has put two notes from the Nobel Prize-winning prodigy up for auction. And you’ll never guess what he wrote.

As the story goes, Einstein was on a 1922 speaking tour in Tokyo when a Japanese courier delivered a message to him at the Imperial Hotel. Upon realizing that he didn’t have enough change to tip to messenger, he whipped out a pen and scribbled down some life tips, instead.

Those two pieces of advice? First, “A quiet and modest life brings more joy than a pursuit of success bound with constant unrest,” he wrote in German on Imperial Hotel Tokyo stationary. “Where there’s a will, there’s a way,” reads the second, written on a blank piece of paper.

As Einstein handed over the advice, he added a small quip: “Maybe if you’re lucky those notes will become much more valuable than just a regular tip,” the seller, who is a relative of the courier, claims.

There’s definitely some genius behind that simple wisdom. But if you really want to test your brains, start with the Einstein riddle that only two percent of people can solve.