A motorized wheelchair offers freedom of mobility to its user, and famed astrophysicist Dr. Stephen Hawking was no exception.

Hawking died at his home in Cambridge, England, on the morning of March 14, 2018 at the age of 76. An auction of some of his personal items earlier this month, including one of his wheelchairs, brought in prices that exceeded expectations, The New York Times reported.

The final price for the old red motorized wheelchair, which was sold to an undisclosed bidder, was about $390,000. That was more than 15 times the pre-sale estimate from Christie’s, per the times.

The online auction that began Oct. 31 and ended Nov. 8 offered a total of 22 items from Dr. Hawking’s estate. All of the items were sold. The total amount raised by the auction, about $1.8 million, was about seven times as much as Christie’s had predicted.

“The results of this remarkable sale, with more than 400 registered bidders from 30 different countries, demonstrate the enormous admiration and affection with which Stephen Hawking was viewed around the world,” said Thomas Venning and James Hyslop of Christie’s,

Other items at the auction included personal possessions of Sir Isaac Newton, Charles Darwin and Albert Einstein. Those items sold for more than $2.3 million.

Dr. Hawking used the wheelchair that was sold at the auction during the late 1980s and early ’90 until his degenerative disease, amyotrophic lateral sclerosis, or Lou Gehrig’s disease, made it so he could no longer steer the wheelchair with his hands.

Another bidder spent more than $760,000 on Dr. Hawking’s signed 1965 Ph.D. thesis, “Properties of Expanding Universes,” about the origins of time and space.

Proceeds from the wheelchair sale will benefit the Stephen Hawking Foundation and the Motor Neurone Disease Association; proceeds from other items, including a bomber jacket, a script from an episode of the Simpsons, and a copy of his book “A Brief History of Time,” marked with his thumbprint as a signature, will go to his estate.