According to historical records, during Zhuge Liang's Northern Expedition, Puyuan created a "wooden cow" to transport food and grass for the army. At that time, the wooden cow was a special unicycle. The unicycle is characterized by its simple structure. The front ends of two handlebars are mounted on a wheel, and the handlebars are connected by a cross bar to form a frame on which people or articles are seated, and vertical guard wheels are arranged on both sides of the wheel. Driving is flexible and light. Generally, as long as one person pushes or pulls in front, people can carry goods. Driving on narrow roads, its traffic volume is several times larger than human load and animal load.