Tipping is always a minefield for me. Staying in Europe for a bit, the system of when, where, and how much to tip is vastly different from that in the United States. But when it comes to dealing with hotel staff members, I’m more than happy to show my appreciation for assistance and knowledge. On the other hand, these days, I don’t usually carry cash with me, and, instead, I rely on the touchless pay systems of my mobile phone. Other travelers throughout history have encountered similar potentially awkward situations of not having ready cash to tip staff when a service is rendered.

Take the case of Al.

Al was born in Germany in 1879 and had become a academician and professor. His research and work had gained a reputation, and, because of this, he was traveling in Japan an speaking at some universities on his specialty subject in early November, 1922. He and his wife were staying at the Imperial Hotel in Tokyo while his lectures were going on at the nearby national university. The couple were in the lobby, enjoying a drink, when a bellboy at the establishment came up to him and handed him a telegram. We aren’t sure that Al didn’t have change–some versions of this story say that the bellboy refused a tip in the first place–but for whatever reason, the young man didn’t receive money for his service to Al and his wife.

Looking around, Al saw some Imperial Hotel stationery sitting on a nearby table. Taking a fountain pen from his coat pocket, he grabbed two sheets of the stationery and scribbled two notes and gave them to the bellboy. The first note read, in German, “A calm and modest life brings more happiness than the pursuit of success combined with constant restlessness.” The second note said, “Where there’s a will, there’s a way.” And then Al signed and dated both notes.

The bellboy looked somewhat confused. It’s unclear if the young man knew who Al was at the time, in fact, and that means that we can understand his confusion. It seems that Al sensed the bellboy’s hesitation at receiving the notes, so he tried to explain to him. “You keep those,” Al told him. One day, he said, you can sell those notes and they’ll be worth more money than any tip I could give you as a tip today.

Fast-forward to 2017, a full 95 years after Al gave the bellboy the pair of notes as a tip. At an auction in Jerusalem, the first note was sold to a private European collector for $1,560,000. The second, shorter one, sold for almost $250,000. Turns out that Al was right. The notes were worth more than any tip he could have given the bellboy. Interestingly, the notes had been passed down from the bellboy to his grand nephew, who was by then living in Germany. Who was this man whose autograph and handwriting could bring so much money at auction?

Seems that besides knowing about physics, Albert Einstein knew a little something about the value of autographs as well.