Masters of LOGIC

I was just thinking about cd's and magnetic tapes when a quirky problem came to my mind. How much physical space do we really need to store a particular amount of information? Maybe CS/IT guys have a straightforward answer for this.

Anyways, how would you store, say a three page letter on a metre stick? (A one metre long thin cylindrical metal stick). Write on it? Of course you can write in very small size letters. But is there any other method? Make some marks or something. What is the most bizarre method? Suppose matter is continuous and you have technology to achieve any level of precision you want. Suppose we have machines that can read (and make) the minutest of marks with infinite degree of precision.

Now can you encode an entire book on that rod (in a retrievable format, of course) by making a single mark on it?