It never ceases to amaze me how even the most sophisticated Romans, such hardheaded realists in so many respects, were at the same time given to believing the craziest of old wives' tales.
Here is one I particularly like, from Ammianus Marcellinus' History of the Later Roman Empire. I have included an entire paragraph for context and bolded the key portion:
Now the aforesaid Barbatio was a somewhat boorish fellow, of arrogant intentions, who was hated by many for the reason that, while he commanded the household troops under Gallus Caesar, he was a perfidious traitor; and after Gallus' death, puffed up with pride in his higher military rank, he made like plots against Julian, when he became Caesar; and to the disgust of all good men he chattered into the open ears of the Augustus many cruel accusations. He surely was unaware of the wise saying of Aristotle of old, who, on sending his disciple and relative Callisthenes to King Alexander, charged him repeatedly to speak as seldom and as pleasantly as possible in the presence of a man who had at the tip of his tongue the power of life and death. And it should not cause surprise that men, whose minds we regard as akin to the gods, sometimes distinguish what is advantageous from what is harmful; for even unreasoning animals are at times wont to protect their lives by deep silence, as appears from this well-known fact. The geese, when leaving the east because of heat and flying westward, no sooner begin to traverse Mount Taurus, which abounds in eagles, than in fear of those mighty birds they close their beaks with little stones, so that even extreme necessity may not call forth a clamour from them; and after they have passed over those same hills in speedier flight, they cast out the pebbles and so go on with greater peace of mind.
The photo, by the way, is from a very amusing article entitled Canada Geese Put One Over on American Eagle.