MissingSourceFile Error

I launched the webrick server to work on a Rails project today and kept getting the following error when trying to access the site via http://localhost:3000:

MissingSourceFile (no such file to load -- ./../config/../config/routes.rb)

Turns out it matters were you launch the webrick server from. I had run: ruby ./server from the script folder instead of running: ruby script/server from the rails application root folder.