A good option for sending cash via courier or post is to put it in a book, preferably a softcover. The Plume softcover edition of The Fountainhead has a total of 752 pages, so 377 places to put a single bill -- nearly forty grand if you're using hundreds.
If you use a hardback you might consider hollowing it out. A hardback desk reference set consisting of a dictionary, thesarus, Black's Law and Bartlett's Quotations could be used to move around sixty to eighty grand in hundreds easily.
Of course this might raise a few red flags in the particular instance of moving money to an offshore book, but just generally speaking about mid-size amounts of cash like that books (the kind you read, not sportsbooks) are a good option.
As far as transfers to an from an offshore book, I don't get why more people don't just open an account at a bank offshore and use it as the gateway to and from the book. Simple, cheap, reliable, etc.
Phaedrus