A medicine ball is a weighted, leather ball. It masses in at around 5 kilograms or 11 pounds. The sphere's diameter is usually around 0.6 meters or 2 feet. Medicine balls can often be seen being tossed around in old film clips of 1950's high school gym classes. It is a device used in weight training and general exercise.
While similar apparatti have been used since ancient times, the medicine ball in the form it is today was patented in the 1890's. However, the term medicine ball was not coined until World War I. The moniker's origin was from Navy medics who would fill a leather casing with kapok and rags and have the seamen toss it around in an attempt to combat seasickness and boredom.
Naval ships continued to use medicine balls as a form of entertainment. In 1928, while traveling aboard the USS Utah on a tour of South America, President-elect Herbert Hoover witnessed the crewmen playing a game of bull in the ring, a type of activity where the players formed a circle around a center player, or bull, and toss a medicine ball around in an attempt to keep the bull from getting it. Herbert Hoover played it, took a liking to it, and brought it back with him to the White House. This game became commonly known as Hoover Ball.