Je was op zoek naar: in aspectu virginis mentem esse puram (Latijn - Engels)

in aspectu uirginis mentem esse puram;
it is hard enough to overcome nature

posuitque eas in canalibus ubi effundebatur aqua ut cum venissent greges ad bibendum ante oculos haberent virgas et in aspectu earum conciperen
and he set the rods which he had pilled before the flocks in the gutters in the watering troughs when the flocks came to drink, that they should conceive when they came to drink.