A journal? Or just letter paper?
Discussion
Paper and maybe matching envelopes
You don't need envelopes, you can just put a stamp on a folded up letter or a laser etched piece of hardtack. Skipping the envelope might even stop USPS from reading it, they might only have time to read the stuff that needs to be X-rayed.
I don't mail my letters. They're usually tucked into a gift or jacket pocket or something like that.