A selection of rare and intimate letters from Albert Einstein on everything from God to his son's geometry studies and a little toy steam engine were auctioned Thursday for more than $420,000, far exceeding pre-sale estimates.

The 27 Einstein letters were in both English and German and written longhand and on a typewriter.

Amassed over decades by a private collector, the letters represented one of the largest caches of Einstein's personal writings ever offered for sale.

At the Profiles in History auction, they brought in a total of $420,625, including $62,500 paid for Einstein's letter to his son discussing the connection between his theory of relativity and the atomic bomb.

Joseph Maddalena, founder of Profiles in History, said, "We all know about what he accomplished, how he changed the world with the theory of relativity. But these letters show the other side of the story. How he advised his children, how he believed in God."

In one letter, Einstein urged one of his sons to get more serious about geometry. In another, he consoled a friend who recently discovered her husband's infidelity. In still another, to an uncle on his 70th birthday, Einstein recalled how the toy steam engine the uncle gave him years ago had prompted a lifelong interest in science.

On the issue of God, Einstein dismissed the widely held belief that he was an atheist.

"I have repeatedly said that in my opinion the idea of a personal God is a childlike one," he wrote to a man who corresponded with him on the subject twice in the 1940s. "You may call me an agnostic, but I do not share the crusading spirit of the professional atheist. ... I prefer an attitude of humility corresponding to the weakness of our intellectual understanding of nature and of our own being."

"These are certainly among the most important things I've ever handled," Maddalena said. "This is not like a Babe Ruth autograph or a signed photo of Marilyn Monroe. These are historically significant."

The Associated Press contributed to this report