“Just as Archimedes had found the volume of an irregular shape by measuring the volume of water it displaced, so Galileo discovered a practical solution to the problem of finding the area under a curve. In the absence of geometric and algebraic tools to calculate the area, he would plot his curve, then cut it out and weigh the paper. By comparing the weight with the weight of a piece of paper of known area, he could work out the area of his curve.”

Rooney, Anne. The Story of Mathematics. Arcturus, 2009. p146.