The Mayans and the Aztecs were the first ones to get rubber from trees. To get the sap from a rubber tree, you make a thin diagonal cut to take off a bit of bark. The latex sap drips out, like blood would come out of a small cut. The latex drips into a bucket. After around six hours, it stops flowing. During this six hours, a gallon (3.7 liters) of latex drips out. The next day, you can make another cut to get more latex.
Early peoples would let the latex dry and they would make balls from it. They’d dip their feet in it, let it dry, dip their feet again, and let it dry, etc., until the dried latex was thick enough to be shoes. They’d peel the shoes off their feet and hold them in smoke to make them stronger. Nowadays, we mix natural rubber latex with sulfur and lead oxide to make it harder, so that it can be used for a wide range of products.