Sources

The first time I read this, it was quoted at the beginning of Edgar Allan Poe's "Murders in the Rue Morgue". Sayers quoted it too. But later I read it in the source, Sir Thomas Browne's "Urn-Burial":

What Song the Syrens sang, or what name Achilles assumed when he hid himself among women, though puzling Questions are not beyond all conjecture. What time the persons of these Ossuaries entered the famous Nations of the dead, and slept with Princes and Counsellours, might admit a wide solution. But who were the proprietaries of these bones, or what bodies these ashes made up, were a question above Antiquarism.

But who was Browne quoting? For that, we go to Laudator Temporis Actii on "The Pleasures of Pedantry":

Tiberius was fond of questions like this, according to Suetonius (Life of Tiberius 70.3, tr. J.C. Rolfe):

Yet his special aim was a knowledge of mythology, which he carried to a silly and laughable extreme; for he used to test even the grammarians, a class of men in whom, as I have said, he was especially interested, by questions something like this: "Who was Hecuba's mother?" "What was the name of Achilles among the maidens?" "What were the Sirens in the habit of singing?"

maxime tamen curavit notitiam historiae fabularis usque ad ineptias atque derisum; nam et grammaticos, quod genus hominum praecipue, ut diximus, appetebat, eius modi fere quaestionibus experiebatur: "quae mater Hecubae, quod Achilli nomen inter virgines fuisset, quid Sirenes cantare sint solitae."

Knowing this makes me very happy. So I guess I too am a pedant!

Wikipedia on "Urn Burial"