“The house is a piece of art,” says Paul Maranger, of Sotheby’s International Realty. “When buyers go into the house the first reaction is a sense of awe."

Stewart, whose other passion apart from maths was music, had two requirements he wanted the architects to meet: he wanted a house that was based on curves - which would require calculus in the design - and he wanted it to include a concert space.

After meeting many top architects, he commissioned the Canadians Brigitte Shim and Howard Sutcliffe to come up with a design. Building work began in 2003 and finished in 2009. The house, whose address is 194 Roxborough Drive, Rosedale, Toronto, cost more than US$23 million.

“I think it’s one of the most important private houses built in North America in a long time,”Glenn Lowry, director of New York’s Museum of Modern Art, told The Wall Street Journal. “The curved walls make it almost impossible to relate it to spaces that you know. It’s one of the most remarkable houses I’ve ever been in."

“I think the person who buys this house will be someone who likes to entertain,”says Paul Maranger. “Not many houses were built as a concert hall. It was designed for a traffic flow of a couple of hundred people."

Stewart studied at Stanford and Toronto universities, and was a postdoctoral fellow at the University of London researching harmonic and functional analysis. By the late 1970s he was back in Canada, at McMaster University, Ontario, when one day he was approached by two of his students who suggested he write a calculus textbook, since his lecture notes were better than the book they were using.

He started writing. Together with his teaching and research he worked for 13 hours a day until his first book was finished seven years later. His dedication paid off - it was the first of about 30 books that catapulted him into the bestseller lists.

“He was the rock star of the calculus world. His books were number 1 in China. He was for years number 1 in the US,” says Paul Maranger.

Don’t be surprised if you have never heard of him, though. Stewart’s books are generally only known by students studying maths, or maths-based subjects. And some of his books cost well over US$150.

Stewart was diagosed with a rare blood cancer in 2013. He carried on writing calculus text books until his death.

Maranger says Stewart was a passionate about his work: “The bookshelf had three distinct areas: far left was the books he wrote, centre was the books he collaborated on and the right was the competition."

The house was a lifetime project and everything in it was custom built. The floors were laser cut in France.

From the windows you cannot see any other house.

Maranger says: “He thought electrical outlets were ugly so you can't see any. If standing in the middle of the room you cannot see any plugs."

Stewart was active in LGBT campaigning and frequently gave his house over for fundraisers. Both Philip Glass and Steve Reich have played there. Before he died he said he hoped his house would continue to be used for these sort of events.

Let’s hope a buyer is found who has a love of music, sharing - and mathematics.

The Guardian