Bava Batra 101 - Selling Burial Plot
In the times of the Mishna it was customary to bury the dead in catacombs. A subterranean chamber would be dug first. Recesses were then dug into the walls of the chamber, and the dead were placed in these recesses. Catacombs serving as family burial places contained several chambers with multiple recesses.
One who sells a lot to his fellow to build a catacomb for him upon it, or one who accepts a contract to make such a catacomb, must adhere to the following standards: each crypt has to be 4x6 amot; he must open eight recesses, three on one side, three on another, and two in the middle opposite the door; the length of each recess must be eight amot, and the height must be seven hand-breadths. Rabbi Shimon says, 4x8 amot. An amah (arm) is between 1.5 and 2 feet.
Art: Felix Benoist - Catacombs of San Calixto in Rome