<p>This interesting way of looking at numbers as piles of rocks was suggested by Paul Lockhart in his book <em><a href="https://www.amazon.com/Mathematicians-Lament-School-Fascinating-Imaginative-ebook/dp/B003VPWWFW/ref=sr_1_1?crid=JBE9XLGYLRXA&keywords=a+mathematician%27s+lament&qid=1696179607&sprefix=a+mathematician%27s+lamen%2Caps%2C131&sr=8-1" target="_blank">A Mathematician's Lament</a>. </em>I learned about it in Steven Strogatz's book <a href="https://www.amazon.com/The-Joy-of-x-Steven-Strogatz-audiobook/dp/B07VGN5VPH/ref=sr_1_1?crid=2X541UNIB9UUH&keywords=the+joy+of+x&qid=1696179632&sprefix=the+joy+of+x%2Caps%2C130&sr=8-1" target="_blank"><em>The Joy of x</em></a>.</p>