It was an unusual request from Khalid Sheikh Mohammed to his CIA captors: would they mind if he kept himself occupied by designing a vacuum cleaner?
The self-confessed mastermind of the 9/11 terrorist attacks in the US, who has a degree in mechanical engineering, was granted his request to keep him sane.
According to the Associated Press (AP), Mohammed made his plea while imprisoned in a secret CIA prison in Romania a decade ago.
The agency officer in charge of the prison called CIA headquarters and the request was approved.
Khalid Sheikh Mohammed, who is now being held in Guantanamo Bay, had endured harsh interrogation techniques during his imprisonment, and the Americans had an interest in protecting his mental health in case he stood trial one day.
“We didn’t want them to go nuts,” an anonymous former senior CIA official told AP.
The prisoner used the web to pursue his studies, but his blueprint for cleaner carpets has not been revealed. What has been made public is Mohammed’s liking for JK Rowling’s Harry Potter series.
After prisoners finished reading books, CIA officers had the delicate task of leafing through the pages to make sure detainees were not passing messages to one another.
On one occasion, Mohammed was caught trying to hide a message about Osama bin Laden’s courier.
The secret prison was shut in 2006 and it is not known how far his plans proceeded.
Mohammed’s military lawyer, Jason Wright, said he was not allowed to discuss the matter.
“It sounds ridiculous, but answering this question, or confirming or denying the very existence of a vacuum cleaner design, a Swiffer design, or even a design for a better hand towel, would apparently expose the US government and its citizens to exceptionally grave danger,” he said.
Mr Wright said he often discussed “modern technological innovations” and the “scientific wonders” of the Koran with Mohammed, whom he described as “exceptionally intelligent”.
He added: “If he had access to educational programmes in Guantanamo Bay, such as distance learning programmes, I am confident that in addition to furthering his Islamic studies, he could obtain a PhD in mechanical engineering and very likely patent inventions.”
AP asked the CIA for copies of the vacuum cleaner designs under freedom of information laws.
The CIA said records, “should they exist,” would be highly classified and therefore exempt from ever being released to the public.
Mohammed, an associate of Osama bin Laden, was arrested in Pakistan in 2003 and has been subjected to waterboarding (simulated drowning) and extreme sleep deprivation. He is due to stand trial for the 9/11 attacks.