Coehorn
A coehorn /ˈkoʊhɔːrn/ (also spelled cohorn) was a portable mortar developed in the Netherlands by Menno van Coehoorn in 1674 and in use from the seventeenth to the mid nineteenth centuries. Unlike larger, heavier mortars, the coehorn was designed to be movable by as few as four men. By the time of the American Civil War, it was in service with both armies in twelve (4.62") and twenty-four pound varieties.
Unlike most other contemporary mortars, the coehorn fired a powder-filled, time-fused shell at a relatively short range. Range could be altered by adding to or reducing the amount of powder loaded behind the shell. Its usually small powder charge and slow muzzle velocity meant that the shell's high, arching flight could be easily observed from ground level.
See also
Media related to Coehorn mortars at Wikimedia Commons