Einstein scribbled his theory of happiness in place of a tip. It just sold for more than $1 million.

He is known as one of the great minds in 20th-century science. But this week, Albert Einstein is making headlines for his advice on how to live a happy life — and a tip that paid off.

In November 1922, Einstein was traveling from Europe to Japan for a lecture series for which he was paid 2,000 pounds by his Japanese publisher and hosts, according to Walter Isaacson’s biography, “Einstein: His Life and Universe.” During the journey, the 43-year-old learned he’d been awarded his field’s highest prize: the Nobel Prize in physics. The award recognized his contributions to theoretical physics.

News of Einstein’s arrival spread quickly through Japan, and thousands of people flocked to catch a glimpse of the Nobel laureate. Impressed but also embarrassed by the publicity, Einstein tried to write down his thoughts and feelings from his secluded room at the Imperial Hotel in Tokyo.

That’s when the messenger arrived with a delivery. He either “refused to accept a tip, in line with local practice, or Einstein had no small change available,” according to the AFP.

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Instead, Einstein wrote two short notes and handed them to the messenger. If you are lucky, the notes themselves will someday be worth more than some spare change, Einstein said, according to the seller of the letters, a resident of Hamburg, Germany who is reported to be a relative of the messenger.

Those autographed notes, in which Einstein offered his thoughts on how to live a happy and fulfilling life, sold at a Jerusalem auction house Tuesday for a combined $1.8 million.

“A calm and modest life brings more happiness than the pursuit of success combined with constant restlessness,” reads one of the notes, written in German on the hotel’s stationery.

It just sold for $1.56 million. The letter had originally been estimated to sell for between $5,000 and $8,000, according to the Winner’s Auctions and Exhibitions website.

Gal Wiener, chief executive of the auction house, said the bidding on that note began at $2,000 and escalated for about 25 minutes, the Associated Press reported.

“When there’s a will, there’s a way,” read the other note, written on a blank sheet of paper. That note sold at auction for $240,000 and was initially estimated to sell for a high of $6,000.

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Neither the buyer’s nor the seller’s identity has been made public.

Roni Grosz, the archivist overseeing the Einstein archives at the Hebrew University of Jerusalem, told the AFP that the notes help uncover the innermost thoughts of a scholar whose public profile was synonymous with scientific genius.

“What we’re doing here is painting the portrait of Einstein — the man, the scientist, his effect on the world — through his writings,” Grosz said. “This is a stone in the mosaic.”

Einstein was among the founders of the Hebrew University of Jerusalem and gave the university’s first scientific lecture in 1923. He willed his personal archives, as well as the rights to his works, to the institution.

Back in 1922, Einstein six-week tour of Japan was a huge success.

“Close to twenty-five hundred paying customers showed up for his first talk in Tokyo, which lasted four hours with translation, and more thronged the Imperial Palace to watch his arrival there to meet the emperor and empress,” Isaacson wrote.

The country also left a strong impression on him.