Srinivasa Ramanujan's first famous letter in original format (manuscript except for the 1st page) to Prof G H Hardy dated 16 January 1913. He sent 120 theorems in 10 pages. This is really a treasure. 
Srinivasa Ramanujan's first letter. Theorems on Prime numbers, Integrals, modular forms, theta functions, continued fractions, Rogers-Ramanujan identities, integral transforms etc.
Prof. Hardy's response: "I had never seen anything in the least like this before. A single look at them is enough to show they could only be written down by a mathematician of the highest class. They must be true because no one would have the imagination to invent them."
