When W/Ds 1st came onto the scene, we had to experiment with anything that may provide enough surface area (before all the scintered glass and other bio-media became available).
At first, everyone used crushed up lava rock. A little later, we started seeing all kinds of things used to provide surface area for BB. For years, I used those green plastic army men toys and the monkey pieces from Barrel-O-Monkies. They worked fine until new materials became available that contain tons more surface area than these hard plastic toys.