Back in the day, before Keanu Reeves was Neo, he was that dude in Johnny Mnemonic. He had some astounding amount of data (100GB was big once) plugged into his head and uploaded. The purpose of this was so he could act as a courier for a third party to transport data and prevent if from being stolen. He would additionally act as escrow service to receive payment for the sale of said brain-data.
Fortunately with the advent of cryptocurrencies, we don't need Keanu Reeves to transfer our data OR escrow our value exchange anymore. You too can create and store a wallet that could be stored in your head. Here's how:
Create a wallet that has a seed key (Electrum, Blockchain.info, Bread Wallet, etc.) Jot down the seed words on a little scrap of paper. Stare at the paper. Eat the paper. No not really. You need to learn how mnemonics works for this to make sense.
Some quick sciency stuff: Your brain's memory function works best when it makes linkages or connections between different things. It also tends to remember things that are out of the ordinary, or novel. If you combine the process of making concepts interact with other concepts in extraordinary fashions, you can create powerful linkages in your brain that can be solidified in a matter of minutes, not hours or days. For example, lets take the words of this example seed: carry, wheel, about, reason, flavor, require, drastic, country, weapon, aim, extra, genre, maid.
The first word, I would visualize me carrying something very large around. Likely, since the second word is somewhat difficult to visualize, I would visualize myself carrying around giant wheel. Next, I would think of that giant word "about" spinning around on a giant tire or wheel. Then the wheel would start carrying on a Socratic debate to discuss reason. Hopefully, you're starting to get the picture (Hah! get it?).
Each word must do something absurd in your brain, and it must interact with the previous and following word. In fact, its sort of like the blockchain in that each block has a tie to its previous block on back to the beginning.
Each instance you do this, you will get better at remembering the linkage, but more importantly why they are linked together. Eventually you will get to the point where you can select a word at random and visually see how it connects to the word before and after it. At this point, you are ready to impress that guy/girl at the bar (read: make awkward) with your new ability to conjure up your net worth in a wallet because you memorized some string of words. If this guy/girl doesn't see why being able to carry your entire net worth in your head securely is a pretty big deal, you may not want a future with this person anyway.
I've already done this with one of my wallets and it's nice to know I can recall that wallet at any time, even months after the initial memorization with a few updates and linkage practice a few times a month. Enjoy!