When the curator Clarisse Colliard asked the Swiss collector Thierry Barbier-Mueller, “Do you even know how many chairs you have?,” he didn’t have an answer. When she told him he had more than 300, Barbier-Mueller was stunned. He had never counted his chairs—because he hadn’t set out to build a collection.

Barbier-Mueller died of a heart attack on January 24, at age 62. His chair collection, which now comprises more than 650 pieces, is one of the world’s largest.

Collecting ran in Barbier-Mueller’s blood. In 1908, his great-aunt Gertrud Müller was still a minor when she acquired Vincent van Gogh’s controversial Portrait of Trabuc, an Attendant at Saint-Paul Hospital. In the 1930s, his grandfather Josef Müller bought a Cuno Amiet at age 20, which he hung on the wall of his shabby student apartment, in Zurich. In 2000, his mother, Monique, gave way to the questionable charms of Jeff Koons’s open-legged sculpture Woman in Tub.

Barbier-Mueller started collecting in his 20s. To purchase the Georg Baselitz painting Eagle (1978), he negotiated an installment plan with the Swiss art dealer Ernst Beyeler—then bought a second Baselitz from Beyeler before he’d finished paying for the first. Though Barbier-Mueller’s mother wasn’t talkative, it was a tacit sign of approval when she allowed him to hang Eagle in her home’s entrance.

The chair collection started in the 1980s. Outlandish designs by artists such as Ron Arad, Tom Dixon, and André Dubreuil kicked things off; later came chairs by Mary Heilmann, Maria Pergay, and Richard Tuttle. Functionality was never interesting to Barbier-Mueller. These were “Do not sit” chairs—sculptures as well as objects. Though early acquisitions were carefully curated, Barbier-Mueller’s whims soon got the better of him. “It was like a thread that you pull and unwind slowly at first, with curiosity and caution,” he wrote, “then with increasing speed, faster and faster, and finally, with conviction and freneticism.”

In The Spirit of Chairs, a glossy volume that accompanies the exhibition “A Chair and You,” curated by Robert Wilson and on at the mudac, in Lausanne, a large portion of the Barbier-Mueller collection has been photographed. “There are only two lines in the world,” says Wilson, “there’s a straight line and a curved line.” Here’s a chance to study the way lines add up to a chair. —Elena Clavarino

Elena Clavarino is the Senior Editor for Air Mail