> "If the manual had been designed today, documents like this wouldn't exist. They'd be nested within dense file trees, stored in data centers in anonymous buildings in rural parts of the world, and accessed through individual computers."

They do exist, and thanks to the internet, are more easily found than ever. Many companies post their design guidelines, even if no external parties will ever use them beyond looking at the final products:

https://developer.nike.com/nikefuel/brand-guidelines.html http://hannahkimdesign.com/mcd_styleguide/ http://guidelines.usability.gov/

And some that are used by people outside of the organisation:

http://www.google.com/design/spec/material-design/introducti... https://developer.apple.com/library/ios/documentation/UserEx...