Google once bought $32,000 in magnets from Home Depot for a project (GOOG, GOOGL)

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Google Cardboard turns smartphones into makeshift VR headsets, and over 10 million of the inexpensive headsets have been shipped, according to Google.

But once upon a time, in 2014, it was a nascent project at Google, with employees putting together the first run of devices with parts bought from a Silicon Valley Home Depot. 

Google's VP of Virtual Reality Clay Bavor shared the original invoice for $32,592 of magnets at Home Depot on Wednesday:

Google Cardboard uses a magnet on the headset's right-hand side as the headset's main button. The magnet moves the compass inside your phone, which registers as a click of sorts.

At the time, the project description was simply "magnets," according to the invoice. 

Google Cardboard was first revealed to the public in 2014, when it was given to attendees at Google's annual conference.

At the time, some people thought it was a joke. But three years later, it's likely the virtual reality experience most people have had the chance to try. Google says that there have been 160 million downloads of Cardboard apps on its app store, and companies like the New York Times have sent them to their subscribers. 

And it all started with an engineer who wasn't afraid to put a massive purchase order on their Visa.