History of the Peloponnesian War
Thucydides
Thucydides. The history of the Peloponnesian War, Volume 1-2. Dale, Henry, translator. London: Heinemann and Henry G. Bohn, 1851-1852.
They despatched orders also through the rest of the Peloponnese to bring up their reinforcements to Pylus as quickly as possible and sent for their sixty ships at Corcyra. These having been hauled over the isthmus of Leucas, and having so escaped the observation of the Athenian fleet at Zacynthus, reached Pylus; the land-forces also having by that time arrived.
While the Peloponnesians were yet sailing up, Demosthenes anticipated them by secretly sending two ships with a message to Eurymedon and the Athenians on board the fleet at Zacynthus to join him, as the place was in danger.