Urorum

Eodem anno Frisii, transrhenanus populus, pacem exuere, nostra magis avaritia quam obsequii impatientes. tributum iis Drusus iusserat modicum pro angustia rerum, ut in usus militaris coria boum penderent, non intenta cuiusquam cura quae firmitudo, quae mensura, donec Olennius e primipilaribus regendis Frisiis impositus terga urorum delegit quorum ad formam acciperentur. id aliis quoque nationibus arduum apud Germanos difficilius tolerabatur, quis ingentium beluarum feraces saltus, modica domi armenta sunt. ac primo boves ipsos, mox agros, postremo corpora coniugum aut liberorum servitio tradebant. hinc ira et questus et postquam non subveniebatur remedium ex bello. rapti qui tributo aderant milites et patibulo adfixi: Olennius infensos fuga praevenit receptus castello cui nomen Flevum; et haud spernenda illic civium sociorumque manus litora Oceani praesidebat.
(Tacitus, Ann. 4.72)

 That same year a people beyond the Rhine, the Frisians, abandoned their peace, more through our rapacity than because they were chafing at their subjection. Drusus had levied from them a modest tribute, taking account of their straitened circumstances: their payment was to be oxhides for military use. However, nobody had paid attention to the firmness or measurements of the hides until Olennius, a man of senior centurion rank who had been appointed to govern the Frisians, chose the skin of the auroch as the yardstick of acceptability. That would even have posed a problem for any other tribes, but in the case of the Germans it was particularly difficult to tolerate in that, while they have woods teeming with huge beasts, their domestic animals are quite small. At first, they were surrendering just the oxen; then it was their lands; and finally it was their wives or children delivered into slavery. From this came rage and protests; and when no relief arrived, war was the solution. The soldiers who were there to take the tribute were kidnapped and nailed to gibbets. Olennius escaped the fury of the Frisians by flight, and was taken in at a fortress called Flevum. There a unit of no mean size, comprising citizens and allies, stood watch over the Ocean coastline. (tr. John C. Yardley)