Plutarch, Demosthenes
Bernadotte Perrin, Ed.

31. Now, a short time before I took up my abode in Athens, the following incident is said to have occurred. A soldier who had been called to an account by his commander, put what little gold he had into the hands of this statue of Demosthenes. It stood with its fingers interlaced, and hard by grew a small plane-tree. [2] Many of the leaves from this tree, whether the wind accidentally blew them thither, or whether the depositor himself took this way of concealing his treasure, lay clustering together about the gold and hid it for a long time. At last, however, the man came back, found his treasure intact, and an account of the matter was spread abroad, whereupon the wits of the city took for a theme the incorruptibility of Demosthenes and vied with one another in their epigrams.

[3] As for Demades, he had not long enjoyed his growing reputation when vengeance for Demosthenes brought him into Macedonia, whose people he had disgracefully flattered, only to be by them justly put to death. He had been obnoxious to them even before this, but now fell under a charge from which there was no escape. A letter of his, namely, leaked out, in which he had urged Perdiccas to seize Macedonia and deliver the Greeks, who, he said, were fastened to it only by an old and rotten thread (meaning Antipater). [4] And when Deinarchus the Corinthian denounced him for this, Cassander¹ flew into a rage and slew the son of Demades as he stood close by his father's side, and then ordered that Demades should be likewise killed. Demades was now learning amid his extremest misfortunes that traitors sell themselves first, a truth of which Demosthenes had often assured him, but which he would not believe.

And so, Sosius,² thou hast the promised Life of Demosthenes, drawn from such written or oral sources as I could find.