The caissons were counterbalanced, the ascending caisson and the descending operating together. The horse follows the caisson carrying the casket. The Pier supporting the main bridge spans is founded on a concrete caisson. The sun broke through the gloom as the coffin was placed on a gun caisson. The casket may or may not be horse-drawn on a caisson. The caisson was also a two-wheeled carriage. An open caisson may fill with water during sinking. There was one caisson for each artillery piece in a battery. Stone was added to the chamber, which caused the caisson to sink. Looking superficially similar to the caisson lock is the shaft lock. In one notorious case, Gould had Tracy in an inescapable deathtrap with a caisson. By 1903, three workers had died while working on the Brooklyn-side tower's caisson. This makes for easy counterbalancing by a fixed weight or by a second caisson. The buoyancy of the lower caisson would make it more difficult to turn the wheel. Pioneering Spirit collided with the caisson of the Yme platform during the removal.