In "In the Midst of Alarms" (1894) by Robert Barr, the author is describing a situation, where a man is going from America to Canada to camp in the forest with his friend, and they were being searched at customs department:
“What’s all this tackle?” asked the burly and somewhat red-faced customs officer at Fort Erie.
“This,” said Yates, “is a tent, with the poles and pegs appertaining thereto. These are a number of packages of tobacco, on which I shall doubtless have to pay something into the exchequer of her Majesty. This is a jug used for the holding of liquids. I beg to call your attention to the fact that it is at present empty, which unfortunately prevents me making a libation to the rites of good-fellowship. What my friend has in that valise I don’t know, but I suspect a gambling outfit, and would advise you to search him.”
And in a previous passage, this american man said:
"Besides, the empty jar will save trouble at the customhouse. I don’t suppose Canadian rye is as good as the Kentucky article, but you and I will have to scrub along on it for a while. And, talking of whisky, just press the button once again.”
He seems to make a sarcastic comment, but I can't get its meaning.