On April 5, 1995, John Wainwright was the first non-employee to purchase a book on the newly-launched Amazon.com, and as he states on Quora.com, the book still shows up in his order history.
"I think I ordered the book over a T-1 connection at work," he wrote. "I was working at Kaleida Labs, the Apple/IBM joint venture, at the time."
Photo of book with original packing slip via Quora.com/John Wainwright