Strabo Geography 11.14.8

[8] There are also large lakes in Armenia; one the Mantiane, which being translated means “Blue”; ¹ it is the largest salt water lake after Lake Maeotis, as they say, extending as far as Atropatia; and it also has salt-works. Another is Arsene, also called Thopitis. ² It contains soda, ³ and it cleanses and restores clothes; ⁴ but because of this ingredient the water is also unfit for drinking. The Tigris flows through this lake after issuing from the mountainous country near the Niphates; and because of its swiftness it keeps its current unmixed with the lake; whence the name Tigris, since the Median word for “arrow” is “tigris.” And while the river has fish of many kinds, the fish in the lake are of one kind only. Near the recess of the lake the river falls into a pit, and after flowing underground for a considerable distance rises near Chalonitis. ⁵ Thence the river begins to flow down towards Opis and the wall of Semiramis, as it is called, leaving the Gordiaeans and the whole of Mesopotamia on the right, while the Euphrates, on the contrary, has the same country on the left. Having approached one another and formed Mesopotamia, the former flows through Seleuceia to the Persian Gulf and the latter through Babylon, as I have already said somewhere in my arguments against Eratosthenes and Hipparchus. ⁶