Exodus 30:2

A cubit shall be the length thereof, and a cubit the breadth thereof; foursquare shall it be: and two cubits shall be the height thereof: the horns thereof shall be of the same.

Foursquare - the meaning of which is, not that it was to be entirely of a cubical form, but that upon its upper and under surface it showed four equal sides. It was twice as high as it was broad, being 21 inches broad and 3 feet 6 inches high. It had "horns;" its top, or flat surface, was surmounted by an ornamental edge or rim, called a crown; and it was furnished at the sides with rings for carnage. Its only accompanying piece of furniture was a golden censer or pan, in which the incense was set fire to upon the altar. Hence, it was called the altar of incense, or the "golden altar," from the profuse degree in which it was gilded or overlaid with the precious metal. This splendour was adapted to the early age of the Church; but in later times, when the worship was to be more spiritual, the altar of incense is prophetically described as not of gold, but of wood, and double the size of that in the tabernacle, because the Church should be vastly extended (Malachi 1:11).