I was reading a passage on the saloon history in North America, in a work titled The Saloon by Gerald Carson, and ran into the following passage:
A good bartender did not drink while on duty. If urged, he would say, "but I will take a mild cigar." This ultra-Colorado is known in saloon history as "the saloon cigar." At the end of the day, it went back into the box it came from, and the barman took credit for it on the cash register. If pushed hard to take something by a very special crony, the bartender would draw a "snit" of beer in a private glass he kept on the work board under the bar. It was about the size of an eye cup. The knowledgeable barman filled it with foam and could put down a hundred if necessary and still not know that he had received a message.
It's the end of the paragraph. I don't really understand the final part, what does it mean by received a message. What message?