I recently came across a (limited) reference to a (2,5) Turing machine implementation that can be represented using chess pieces on a 2D board. I know it is possible to implement a UTM using cellular automata, no specifics were given to the rules or what type of TM this would be.
Does anyone know of an implementation like this? Preferably one you can manipulate 'easily' by hand or in your mind. I'm most interested in rule sets that can be used for arithmetic computation.