One of the titans of 20th-century physics, Richard Feynman deciphered the interplay of fundamental particles and forces. He wrote popular books in which he portrayed himself as a charming scientific rogue, and played a key role in the investigation of the loss of the space shuttle Challenger. While brilliant, he was not perfect. That becomes evident looking at some of his papers that go up for auction on Friday.

Feynman received the Nobel Prize in Physics in 1965 for key insights in understanding the quantum version of electromagnetism, and the medal and citation that came with it is the centerpiece of the auction, conducted by Sotheby’s in New York. But the assorted writings that are also for sale by his family reveal clues into how he worked and thought.

“We tend to have this idea of genius being someone who just sprung out of the womb and had these magical capabilities,” said Cassandra Hatton, the specialist at Sotheby’s in New York who is overseeing the auction. “And Feynman himself denied that fact. He always said, ‘Guys, there’s nothing. There’s no magic here. I’m just somebody who’s very interested and worked very hard and was very curious.’”