Proof that the Gaussian Integral equals the square root of pi.
Hey, I found this really awesome Etsy listing at https://www.etsy.com/listing/291676141/3d-printed-spirograph-drawing
Fran McConville's Harmonograph Page
Image of PrimoGraf Drawing Machine
1 | A Clever Modular Toy That Teaches Kids Kinetic Design | Co.Design | business + design
Sketch Intricate Designs with A Hand-Cranked Drawing Machine | The Creators Project