This week, the Swiss designer Daniel Heer has taken over Mameg, a clothing boutique in Beverly Hills, Calif., to make one of his signature Rosshaarmatratze, or horsehair mattresses. The Heer family has been in the business of making mattresses (and saddles) by hand since 1907, when a great-grandfather established a saddlery in Lucerne, Switzerland, but Daniel, 35, who takes two days to make each mattress, gives the traditional craft his own special touch. He has devised new forms, like his AMPM Daybed, and adopted contemporary textiles for coverings. A Kvadrat gabardine is his preferred fabric. Heer, whose studio is in Berlin and who uses horsehair from the Swiss spinnery Toggenburger & Co., arrived at Mameg with enough of the stuff (of both the blond and brunet varieties) for two mattresses. Put away any ideas you might have of stiff, prickly Victorian horsehair furniture. Horsehair's unique qualities - it's incredibly elastic, soft yet strong, and has an unsurpassed ability to absorb moisture - make it an ideal material for mattresses. So ideal, in fact, that the Queen of England sleeps on one. The hair from a horse's mane provides medium firmness, while the tail hair is much stronger. Braided by the spinnery for ease of transport, the hair must be uncoiled and then separated, a process that takes hours but results in a rather magical cloud of fluff. Heer says the process of stuffing the mattress is intuitive; he knows by feel when the mattress has reached the right degree of firmness. Each of Heer's Rosshaarmatratze takes approximately 33 pounds of horsehair (that's more than 40 horses" worth), and over the course of a day the designer methodically forms the material into three layers that are two feet high, creating the foundation of the mattress. The second day is spent sheathing the foundation in virgin fleece and dressing it in fabric, hand-sewing the edges into rolls and then refining its shape with careful needlework. Heer uses thread pulled from the fabric of the covering to create the tufts or buttons that finish the mattress. New Yorkers will have the chance to see Heer, who also makes leather goods in addition to mattresses and furniture, at work when he sets up shop at Matter on May 19. "I like to be at a place working on a mattress," Heer says. That way people can see the process of making. Otherwise, it becomes too much like a fairy tale with the horses and the mattresses.