The thing about the magnet to degauss them is that you’re not certain that the data can no longer be read. Disc forensic analysis might still be able to retrieve some or much of the data — depending on how thoroughly you’ve degaussed them which, how can you tell unless you perform that forensic analysis. Too much trouble and not enough confirmation for me.
See the company, AccessData Group, now Exterro.
https://www.linkedin.com/company/accessdata-group-inc.
To be certain, I would take a pair of tin snips and cut them in half. Then I’d throw them into a large fire and ensure they are melted.
Quick, easy, and easily confirmable. With those actions I’d be satisfied that they are completely ruined.