Imagine a black box / briefcase cold wallet.
Where you have to unlock the case. Open it. Connect it.
Then enter a pass code and turn two keys.
... and then, 100 years from now, the open up thing (because its ancient junk) and they find a ledger nano taped to the bottom of a sheet of aluminum
Lol possibly with a finger print scanner equipped with pulse reading technology? That way if they just cut off your finger they can't get in as there is no pulse.