Nam quae fiunt in capitibus foramina, per quorum spatia contenduntur capillo maxime muliebri vel nervo funes, magnitudine ponderis lapidis, quem debet ea ballista mittere, ex ratione gravitatis proportione sumuntur, quemadmodum catapultis de longitudinibus sagittarum.
For the holes which are made in the frames (through the openings of which ropes are stretched, made especially of womans hair or of the sinews of animals) are taken proportionately to the amount of the weight of the stone which the balista is to shoot, in accordance with gravity, just as in the case of catapults the length of the arrows furnishes the module.
final_alignments\Vitruvius_Architecture_Book_10.json