The earliest baseballs had a rubber core and were somewhat smaller. This activity will give you an idea of just how bouncy a baseball is. Baseballs Golf Balls Exploratorium staff physicist Paul Doherty compares bounciness of frozen and room temperature baseballs and golf balls. The room temperature balls are on the right in both pictures.
Baseballs have less bounce than tennis balls or golf balls.
This is due, in large part, to their construction, To measure the bounciness of a ball, you can try dropping it from a height onto a hard surface. Try comparing a baseball to a golf ball or a tennis ball. You can also change how a ball bounces by changing its temperature. If you have two baseballs, try putting one in the freezer for an hour and leaving the other at room temperature. Try comparing their bouciness again.