This letter to an unnamed "Immortal Beloved" was found in the personal papers of Ludwig van Beethoven after his death in 1827. Though there's debate over whom the letters were written to, there's not much debate about whether or not Beethoven had it bad for the woman. A snippet:
My bosom is full, to tell you much — there are moments when I find that speech is nothing at all. Brighten up — remain my true and only treasure, my all, as I to you. The rest the gods must send, what must be for us and shall.
Read the rest on Letters of Note. Link