According to this article: https://www.extremetech.com/extreme/134427-a-paper-based-backup-solution-not-as-stupid-as-it-sounds https://www.extremetech.com/extre

According to this article: https://www.extremetech.com/extreme/134427-a-paper-based-backup-solution-not-as-stupid-as-it-sounds https://www.extremetech.com/extreme/134427-a-paper-based-bac... you can cram around 3MB of data (in a reasonably robust way) on the side of a sheet of paper - it is unclear if they mean A4 or Legal, though.