active 16th century Alvar Núñez Cabeza de Vaca, The Conquest of the River Plate…
“ The arroba is a Spanish weight, equal to twenty-five pounds of sixteen ounces each.Continuing the voyage with a fair wind, the governor arrived, on the evening of the 25th October, at a place where the river divides into three channels. One arm forms a great lagoon, which the Indians call the Black River; it runs towards the north into the interior of the country. The other arms, in which the water is of a good colour, reunite a little way further down. ”
