Trichrug, a mountain of Cardiganshire, so called from three small mountains being connected with it, was celebrated not only as a place of fairy resort, but as being once the spot where stood the seat of a giant, whose grave (as some say) is still to be seen, and which is described as fitting any one who will lie within it, whether he be tall or short, and that the person so lying in it will have renewed strength; tradition also relates, that if arms are placed therein they will be immediately destroyed. It is said of this giant, that he invited the neighbouring giants to try their strength with him in throwing stones, and that he won victory by throwing his quoit to Ireland! (a pretty good distance to throw a stone!)
From ‘Cambrian Superstitions’ by W Howells, 1831.
You can see another stone he threw at Llech Bron.