Your average shoebox is 35X23.5X13.5 cm, or 11103.75 cubic centimeters. The density of gold is 19.3 g/cm^3. You can fit 11103.75X19.3 = 214302 grams of gold in a shoebox. One gram of gold right now is $77.78 US. That's 214302X77.78 = over 16.5 million US. There are things significantly more valuable (but not more fungible) than gold, too. The Pi million pill is completely moot. Or just take both, I guess.
You'd need to invest 1mil in a 3000% return stock in order to make 30 mil like the gold option. If you bought fb when it was lowest and sold when it was highest, you'd get 2158% return. There's stuff like Amazon, coca cola, etc. That had much higher % gain but you'll need for that company to exist and then wait for it to explode.
If you already have a lot of money to invest, sure, your strategy might be worth. Otherwise, double gold sounds better.
Smaller quantities shouldn't be too hard to sell. 16.5 million worth would definitely be a bit of a logistical problem. I'm sure a bank would help you out with an amount that large.