Although often illustrated today, the "Seven-Ball" side chair remains one of the great enigmas of 20th-century design. The chair has never been specifically documented in a publication or photograph of the period. Frequently thought to be a variation of the "Purkersdorf Sanatorium" chair, it is similar to a settee that appeared in a 1906 J. & J. Kohn sales catalogue. The striking, yet supple lines accented by the seven spheres became almost a signature style for Hoffmann. Quite likely, the design evolved out of the need for knobs at the leg joints in order to reinforce them.