If you want it to stand the test of time, use other methods that have provably stood the test of time, like a book. You know that will work. You do not know anything currently digital will work. If this is important to you, I wouldn't mess around with "high tech" solutions. It's a complete gamble and relies on too many different components to work, whereas a book you just have to know how to read. The world can be in another dark age and it will still work. At least while there is light out.