A great deal of the work of the post office would then be to regulate the use of these personal television channels. Much of the information now sent by mail could be sent through the air on the personal channel, to be viewed in the home or to be printed out for a more or less permanent record. …

Very likely there will be a signal light to indicate that a message is waiting to be viewed. When the personal channel is then activated, each item stored will be displayed in turn. Each can be scanned and erased, scanned and temporarily returned to storage, or scanned and printed out, after which the next item would appear. It will be very much like going through one’s mail today, with its mixture of personal items and advertising, in which some are discarded, some put aside, and some filed.

— Isaac Asimov, “The Individualism to Come,” New York Times, Jan. 7, 1973

In 1495 Leonardo da Vinci devised a mechanical knight that could sit up, open and close its arms, move its head on flexible neck, and open its visor. The plans have been lost, but we know it was made of wood, brass, and leather and operated by cables, possibly driven by a water wheel. The Duke of Milan displayed it at a pageant near the end of the 15th century, perhaps at the wedding of his niece.

Roboticist Mark Elling Rosheim built a working replica of the knight in 2002 using the sketches that remain, detailed in his book Leonardo’s Lost Robots. He thinks it may have been designed to accost an unwary visitor by remote control. “It is almost like something one would find in an old time amusement park, a piece for the scary haunted mansion or tunnel of love — or a labyrinth, which was the 16th century equivalent. The Knight would be excellent at grabbing someone with its arms in a bear hug. … Perhaps the visor would rise, revealing a hideously contorted, sculpted face.”

“Perhaps the great mystery surrounding this lost robot of Leonardo can be summed up by the master himself in the giant scrapbook known as the Codex Atlanticus. In the sheets for this project, we read an incomplete sentence with which Leonardo tried out his pen: ‘Tell me if ever, tell me if ever anything was built in Rome …’ Leonardo may be expressing his frustration and anxiety about a project near and dear to his heart that because of external pressures could not be born.”

British ironmonger John Chell patented this “hand guard for use in cutting bread” in 1904. Each finger is enclosed in a steel helix that leaves it free to flex but protects it from a knife slip.

Presumably you could also use it to fight crime.

I don’t think this was ever built — in 1904 engineer Hiram Stevens Maxim designed an amusement with a rotating parabolic floor “for producing illusionary effects”:

With such a contrivance when persons enter the hollow sphere they will not be able to tell whether it is revolving or standing still and by reason of the parabolic floor, persons near the outer edge would, to the persons standing near the centre, appear to be walking with their heads directed inward. When the sphere revolves some curious phenomena will be obtained in walking outward and inward on such a floor, and the throwing of a ball from the centre outward and vice versa will move in an unexpected direction that will be very puzzling to the people in the sphere.

Fig. 3, below, shows the perspective from the edge of the floor as it rotates. If mirrors were positioned overhead, as in Fig. 4, “people could then be made to appear to be walking all over the inside of the sphere with their heads pointing inward and their feet pointing outward.”

Pauline Klaws patented this “appliance for assisting the hearing” in 1902. “It is designed to be worn at lectures, concerts, theaters, and meetings by persons having defective hearing and by the people generally who at such entertainments or meetings, particularly large meetings, are unable or have difficulty in hearing a speaker.”

By 1993 this had evolved into the version below, patented by Mark Tilkens, who found it “particularly useful in hunting of game such as deer, to enhance a person’s ability to hear noises which otherwise may be drowned out by background noise.”

Horses are difficult to manage onstage, so in 1901 music hall performer Alexander Braatz invented this ingenious alternative. The actor’s own legs masquerade as those of his horse, and a system of levers and cords moves the hind legs as well.

False human legs are attached at each side to give the appearance that the performer is mounted; his real feet “are advantageously covered by large clumsy hoof-like coverings.” I suppose you could even race these things between rehearsals.

In 1914, Russian physicist Boris Weinberg proposed an electromagnetic vacuum train that could move an individual passenger from New York to San Francisco in half a day. Reasoning that air resistance and friction are the greatest enemies to speed, Weinberg envisioned using electromagnets to suspend a car in a tube from which the air had been partially exhausted. An individual passenger would lie prone in a 300-pound iron cylinder drawn along by a series of solenoids. New passengers could be introduced into the system through an airlock at a rate as high as 12 per minute, “the whole proceeding being not unlike that of feeding cartridges from a belt or clip to a machine gun.”

Weinberg estimated a maximum speed of 500 mph. “Think what that means!” he wrote in The Popular Science Monthly. “New York would be no more distant from Chicago than it is now from Philadelphia, so far as relative times are concerned. Florida might easily become a kind of winter Coney Island for all New York.”

He built a model of the system at the Technological Institute of Tomsk, but the project never got off the ground (so to speak). One reason may have been the cost: In order to slow the cars gradually, each station would have to be 2 miles long.

In 2004 Thomas Magdi patented a machine for changing light bulbs:

A light bulb changer method and apparatus that contains components that allows for instantly detecting a burned out light, automatically removing the burned out light, and automatically replacing the burned out light with a replacement bulb. The changer operates without human intervention, and can be assembled from a kit having a light fixture, detecting sensor, removing and replacement hardware.

The 23-page patent abstract contains 24 figures diagramming 97 components.

Why is this funny?

“This invention relates to new and useful improvements in an aeroplane of rooster shape.” Well, all right, then. Angel Mateo’s 1930 patent application is remarkably thorough — the wings even flap — but nowhere does the inventor explain why he thinks the world needs such a thing. “The propeller is depended upon to accomplish most of the flying of the device and the wings to assist in the flying and also to simulate a flying rooster.” Perhaps, like a poem, it provides its own reason.