At my last startup, our product required information that didn't exist in the digital world - the table of contents of hundreds of medical books. So I used to spend nights and weekends visiting local Barnes & Nobles and university bookstores pulling down books and manually typing out the table of contents with chapter titles, pages numbers, etc. Quite possibly the most boring job ever! Most bookstores didn't mind my presence, but I did get kicked out of one (thanks Harvard Medical School!). I tried to use OCR and other techniques and it just wasn't accurate enough (this was a decade ago so the tech wasn't quite as advanced as it is now). Eventually the company got big enough where I could have dedicated staff to handle the process, but for a long time it was how I spent my free time.