Plutarch on the Persian envoys
There were many stories invented about Alexander's youth, in which he was supposed already to have shown signs of his future greatness. In section 5 of his Life of Alexander, the Greek author Plutarch of Chaeronea tells several anecdotes, like the following.
The translation was made by Mr. Evelyn and belongs to the Dryden series.
Alexander and the Persian envoys
[5.1] While he was yet very young, he entertained the ambassadors from the King of Persia, in the absence of his father, and entering much into conversation with them, gained so much upon them by his affability, and the questions he asked them, which were far from being childish or trifling
[5.2] (for he inquired of them the length of the ways, the nature of the road into inner Asia, the character of their king, how he carried himself to his enemies, and what forces he was able to bring into the field),
[5.3] that they were struck with admiration of him, and looked upon the ability so much famed of Philip to be nothing in comparison with the forwardness and high purpose that appeared thus early in his son.