The Best Company In The Dining Room

In the last years of high school I read different books about the rules of etiquette. It was interesting, specially, because we did not learn them in the school, and our parents, simple persons, hardly could know many of them.

One of the rules was about the optimal number of the persons at the table during the meals. They had to be not less than 3 and not more than 9. Many years later I read about one scientific research that confirmed that rule from the point of view of our health.

The research said:
Good conversation durin the meal helps to create right athmosphere and conseguently it helps good digestion etc. =good health.
The company at the table has to be not less than 3 persons because 2 persons are not sufficient to maintain the conversation.
The company has to be not greater as 9 persons because too big company can not maintain interesting conversation for ALL the members of the company.

Last time I was in museum I remembered about these rule and told it to Pietro. Pietro thought a little and than said: do you know for how many persons were built the tables in triclinium?
Sincerely I did not know what was that triclinum. Here is the description from a dictionary:

Nell'antica Roma, complesso dei tre letti a tre posti, collocati lungo tre lati della tavola, sui quali si disponevano i commensali per mangiare

In the Antique Rome, it was a complex of 3 beds each with 3 places posted on 3 sides of the table where the guests settled for meals (more or less)

So, this rule has nothing with good health, nor with good conversation, mmm? Vestiges of the Roman past. Look at this picture from Wikipedia

But my mother said us always when we were at the table: The rule is "when I eat I'm deaf and dumb. I'm sure, you know this rule too.
Do you know where comes this rule from?
This rule comes from the monastic life.
When the monks ate in the refectorium of the monastery they had to listen to one of them that read the Bible. Therefore they could not speak in this time.