iPod and iTunes: The Missing Manual, Third Edition
Description: iPod and iTunes: The Missing Manual, Third Edition provides detailed instructions on using iPods and managing music libraries with iTunes, covering features, device management, and media organization
This O'Reilly snippet[1] claims the feature wasn't implemented until 2003, and even then explicitly states it could only store plain text.
EDIT: The Notes app on the touch can import html files, but that doesn't sync up with either rockbox or disk mode.
So I'm completely lost at what mechanic they're referring to. Even if we assume that this was a txt file and not html, that explicitly excludes the first gen iPod.
[0]: https://manuals.info.apple.com/MANUALS/0/MA282/en_US/iPod_cl...
[1]: https://www.oreilly.com/library/view/ipod-and-itunes/0596008...