Strabo Geography 3.4.18

[18] Another practice, not restricted to the Iberians alone, is for two to mount on one horse, so that in the event of a conflict, one may be there to fight on foot. Neither are they the only sufferers in being tormented with vast swarms of mice, from which pestilential diseases have frequently ensued. This occurred to the Romans in Cantabria, so that they caused it to be proclaimed, that whoever would catch the mice should receive rewards according to the number taken, and [even with this] they were scarcely preserved, as they were suffering besides from want of corn and other necessaries, it being difficult to get supplies of corn from Aquitaine on account of the rugged nature of the country. It is a proof of the ferocity of the Cantabrians, that a number of them having been taken prisoners and fixed to the cross, they chanted songs of triumph. Instances such as these are proofs of the ferocity of their manners. There are others which, although not showing them to be polished, are certainly not brutish. For example, amongst the Cantabrians, the men give dowries to their wives, and the daughters are left heirs, but they procure wives for their brothers. These things indicate a degree of power in the woman, although they are no proof of advanced civilization. ¹ It is also a custom with the Iberians to furnish themselves with a poison, which kills without pain, and which they procure from a herb resembling parsley. This they hold in readiness in case of misfortune, and to devote themselves for those whose cause they have joined, thus dying for their sake. ²