"O you, who in some pretty boat, Eager to listen, have been following Behind my ship, that singing sails along Turn back to look again upon your own shores; Tempt not the deep, lest unawares, In losing me, you yourselves might be lost. The sea I sail has never yet been passed; Minerva breathes, and pilots me Apollo, And Muses nine point out to me the Bears. You other few who have neck uplifted Betimes to the bread of angels upon Which one lives and does not grow sated, Well may you launch your vessel Upon the deep sea."

Source: The Divine Comedy.