How to Sort Gmail Messages by Size using Google Docs ?

What do you do when your Gmail account is nearly full? You can either purchase additional storage from Google (they charge $5 per year for 20 GB) or a cheaper alternative is that you scan your Gmail mailbox for messages that contain large file attachments and delete (or forward) all the useless messages to recover precious space.
The problem is how do you find these bulky messages in your mailbox when Gmail doesn’t offer an option to sort and filter messages by size?
In the past, I have shared both software tools and web apps that help you quickly track the space-hogging emails in your Gmail account but there’s a new option now that requires no setup and you don’t even have to grant access to your Gmail account to a third-party for analysis – this option is called Google Docs.