ἐν πέτροισι πέτρον ἐκτρίβων → by grinding stone against stones
adv.
hardly: Ar. and P. σκληρῶς.
securely, firmly: P. and V. βεβαίως, ἀσφαλῶς.
obstinately: Ar. and P. ἀυθάδως, P. σκληρῶς.
