Albert Einstein’s handwritten notes for the theory of relativity fetched a record 11.6 million euros ($13 million) at an auction in Paris on Tuesday. The manuscript had been valued at around a quarter of the final sum, which is by far the highest ever paid for anything written by the genius scientist. It contains preparatory work for the physicist’s signature achievement, the theory of general relativity, which he published in 1915. Calling the notes “without a doubt the most valuable Einstein manuscript ever to come to auction”, Christie’s — which handled the sale on behalf of the Aguttes auction house — had estimated prior to the auction that it would fetch two to three million euros. Previous records for Einstein’s works were $2.8 million for the so-called “God letter” in 2018, and $1.56 million in 2017 for a letter about the secret to happiness.

Bids on Tuesday opened at 1.5 million euros and quickly went past the auctioneers’ estimate.

After a few minutes two bidders were left, battling it out over the telephone in increments of 200,000 euros.

There was no immediate information concerning the identity, or nationality, of the winner.

Around 100 collectors and onlookers turned up for the sale, but all bids were made remotely.