The Bosphorus - Strolling Through Istanbul: The Classic Guide to the City - page 460

There is a dalyan or structure for fanging the swordfish; it is
composed of five or six masts, on the highest of which sits a
man who keeps a lookout for the fish that come in from the
Black Sea. When he sees them drawing near, he throws a stone
into the sea in order to frighten them, wherein he succeeds
so well that they all take the direction of the harbour, where
they think to find security, but fall into the nets laid for them
in the water. The nets being closed, on warning given from
the man sitting in the lookout, the fishermen flock round to
kill them without their being able to make any resistance with
their swords. The fish if boiled with garlic and vineyard herbs
is excellent.
There is still a dalyan at Beykoz that is used to catch diferent
sorts of fish, though no longer the swordfish. The modern method of
catching a swordfish is to harpoon it from a rowboat while it naps on
the surface of the water.
Gyllius is at pains to show that Beykoz was the home of the savage
Amycus, king of the no less savage Bebryces. He insisted on boxing
with any stranger who landed on his coast and, since he was the son
of Poseidon and the best boxer in the world, he always killed his
opponent. At last, however, he met his match in one of the Argonauts,
Polyduces (Pollox), son of Zeus and Leda, who was even better than
he and killed him. he grave of King Amycus was pointed out in
antiquity and it is rather strange, as Lechevalier remarks, that Gyllius
failed to identify it with the Giant's Grave. On the spot where King
Amycus was killed there grew up an insana laurus, an insane bay-
tree, which resembled Banquo's “insane root which takes the reason
prisoner.”
Beykoz has a very extraordinary çeşme in the public square. “This
fountain,” says the Hadika, “has not its equal in beauty in all the
villages of the Bosphorus.” It forms a sort of domed and columned
loggia, very pretty indeed, and quite unlike any other Bosphorus
fountain; its inscription dates it to A.H. 1159 (A.D. 1746) and the
Hadika says it was built under the superintendence of one Ishak Aga,
inspector of the customs.