History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
for they found it easier to elude the guard of triremes when the breeze was from the sea, since then it was impossible for the ships to lie at their moorings off the island, whereas they themselves ran ashore regardless of consequences, as a value had been set upon the boats which they drove upon the beach, and the hoplites would be on watch for them at the landing-places on the island. All, on the other hand, who made the venture in calm weather were captured.
At the harbour, too, there were divers who swam to the island under water, towing after them by a cord skins filled with poppy-seed mixed with honey and bruised linseed; at first they were not discovered, but afterwards watches were set for them.
And so both sides kept resorting to every device, the one to get food in, the other to catch them doing it.
At Athens, meanwhile, when they heard that their army was in distress and that food was being brought in to the men on the island, they were perplexed and became apprehensive that the winter would overtake them while still engaged in the blockade. They saw that conveyance of supplies round the Peloponnesus would be impossible—Pylos being a desolate place at best, to which they were unable even in summer to send round adequate supplies—and that, since there were no harbours in the neighbourhood, the blockade would be a failure. Either their own troops would relax their watch and the men on the island would escape, or else, waiting for bad weather, they would sail away in the boats which brought them food.
Above all they were alarmed about the attitude of the Lacedaemonians, thinking that it was because they had some ground for confidence that they were no longer making overtures to them; and they repented having rejected their proposals for peace.