A sparse yet highly desirable page signed by the Wright Brothers is already selling well in an online auction, which closes September 19.

Katharine's involvement with the Wright Flyer is shrouded in rumour

The simple inscription is believed to be written on a page removed from a Mother Goose's Nursery Rhyme book and reads: "Christmas 1911 to Little Fred". It features both the Wright Brothers' signatures along with a third - the exceedingly rare autograph of their sister, Katharine.

Katharine Wright was a high school teacher, who would later become something of a celebrity after she accompanied her brothers to Europe.

Katharine was asked by Wilbur to join Orville in France in 1909, where she quickly became a star of the social scene. An outgoing personality, the local press were enamoured with her as she provided a refreshing change to her notoriously shy brothers, who were often reluctant to reveal details of their projects.

Her role in the creation of the Wright Flyer remains shrouded in rumour. Suggestions that she may have funded much of the experimentation that led to its design, and even that she may have sewn the wing coverings, are still in circulation today.

However it is known that after Wilbur died in 1912, Katharine took on much of the business responsibilities and became an officer of the Wright Company. She was also awarded the French Legion of Honour in respect of her achievements.

The autographs of both brothers on one piece are highly coveted by autograph collectors, but the addition of Katharine's makes this an extraordinary rarity. Bidding currently stands at $15,919.

Paul Fraser Collectibles has a brilliant set of Wright Brothers aviation photographs, which were previously owned by Charles Stewart Rolls.