Seth,
Those types of wedges were use in the old days by "tie" makers (railroad ties). They were called "gluts" and usually had a steel ring around the top to prevent them from spreading out when being pounded with a large wooden mauls. The initial splitting was started with steel wedges and sledge hammer, but when the narrower steel wedges got buried in split, additional force was added by the gluts. They are hard to come by and are usually displayed in logging museums.
Art Martin