Originally Posted by
LapLap
I remember - but I'm extremely interested in learning from which kind of sources this advice is still sprinkling from.
Good grief ... It's in dozens of guidebooks. I doubt that anyone can tell you the source ... the source might be an edict from a tokugawa era shogun for all I know...
Try googling for "kokorozuke" - I get a pretty good description on Ikyu (an online hotel reservation site):
http://www.ikyu.com/spcl2/kntat/vol13.htm
[See section on "the use of pochi envelopes"]
Guests staying at a ryokan always prepare a pochi envelope and some uncreased notes and pass it over unobtrusively.