How much pressure can mountain bike tires take?
Says on the sidewall of a tyre. Mine says between 40-60psi. They also have it in 'bars' if you like to measure in that.

Check out an example here 
http://www.chainreactioncycles.com/schwalbe-magic-mary-evo-mtb-tyre-super-gravity/rp-prod118255

Says max 50psi.