What vauable things can you carry on you & take across borders?
Precious gems, (or diamond dust for abrasives) are a historic form of portable wealth in a very small portable size. The problem is that cut diamonds & other gems, for instance, have a retail price called "Keystone" which is 7 times more than the wholesale price. Diamond dust & raw diamonds have a much smaller markup as they always come from suppliers & sell "wholesale" to end users.
"Collectibles" including rare birds and animals are problematic unless you have a collector/buyer at the other end who will pay
cash & a high "collector" price. I bought some supposedly very valuable collector
gold coins once, but when I went to sell to dealers, they said, "We are sellers, not buyers" ...They offered me only bullion value which was 1/5th of what they sold similar coins for. I had a similar experience with old oriental rugs. These days, as long as the holding period is very short like 24 hours (when a huge price change is unlikely), the most portable, valuable, anonymous thing is indeed,
crypto. Illegal drugs? I won't comment on that. But not recommended for normal 9non-criminal) folks.
Singapore $10,000 bills are I think, already out of circulation. Swiss 1000 franc notes worth around $1000 USA are pretty good. One million bucks worth will fit in an attache case. But these days it is more sensible to simply transfer any funds from one place to another by means of the many services that will do this for a tiny % fee.
Years ago most securities, especially stocks & bonds could be obtained in non-registered, bearer form, but the good old USA has made this almost totally illegal and these days "bearer securities" are pretty much unobtainable ...P.T.