Source: Stadium Goods 'Ultimate Sneaker Collection' Online Auction, New York, USA - 23 Jul 2019, By: Erik Pendzich/Shutterstock

Bill Bowerman, co-founder of Nike, had been searching for running shoes that gripped the ground without heavy spikes. During breakfast with his wife one morning in 1970, Bill noticed the square grooves in their waffle iron, prompting him to immediately grab some rubber from his lab and pour it into the device. This didn't work as he'd hoped – it just glued the waffle iron shut – but the analogy inspired the studs on the original Nike Waffle Trainer shown here, of which Nike has sold tens of millions of pairs since.