Mining Bitcoin with pencil and paper: 0.67 hashes per day

I decided to see how practical it would be to mine Bitcoin with pencil and paper. It turns out that the SHA-256 algorithm used for mining is pretty simple and can in fact be done by hand. Not surprisingly, the process is extremely slow compared to hardware mining and is entirely impractical. But performing the algorithm manually is a good way to understand exactly how it works.

more here..........http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and-paper.html