I estimate the size of the block is 15cm by 45 cm by 30 cm. Space for the hand estimated to be around 15 cm by 15 cm by 15 cm
Taking into account that the density of granite is 2.75g/cm^3, the weight is around 46.4kg
Shaolin monks are not only famed for their internal art. External arts too.
I've read an article on how the martial arts monks train. They run (5km? forgot) every morning, then do martial arts, including zhan zhuang and techniques. Somewhere in between is breakfast, I forgot when.
Then the "training" most similar to weight training would be carrying buckets of water here and there in the afternoon.
Do note that they are vegetarians.