The slaves too in the olden time took their meal sitting on benches in the atrium, so that the whole familia was present.

This means that the dinner was in those days only a necessary break in the intervals of work, and the sitting posture was always retained for slaves, i.e.
those who would go about their work as soon as the meal was over.
Columella, writing under the early Empire, urges that the vilicus or overseer should sit at his dinner except on festivals; and Cato the younger would not recline after the battle of Pharsalia for the rest of his life, apparently as a sign that life was no longer enjoyable.[443] But after the Second Punic war, which changed the habits of the Roman in so many ways, the atrium ceased to be the common dining-place, and special chambers were built, either off the atrium or in the interior part of the house about the peristylium, or even upstairs, for the accommodation of guests, who might be received in different rooms, according to the season and the weather.[444] These _triclinia_ were so arranged as to afford the greatest personal comfort and the best opportunities for conversation; they indicate clearly that dinner is no longer an interval in the day's work, but a time of repose and ease at the end of it.

The plan here given of a triclinium, as described by Plutarch, in his _Quaestiones conviviales_, Lectus medius.
+--------------------------------+----------------+ Chief | | | Guest | | | Lectus | | | Summus +-----------------+--------------+ | H | | | | | | | | Lectus | | Mensa | | Imus | | | | | +--------------+ | | | +----------------+ | | | | | | | | +-----------------+ PLAN OF A TRICLINIUM.
will show this sufficiently without elaborate description; but it is necessary to notice that the host always or almost always occupied the couch marked H on the plan, while the one immediately above him, i.e.
No.

3 of the _lectus medius_, was reserved for the most important guest, and called _lectus consularis_.

Plutarch's account, and a little consideration, will show that the host was thus well placed for the superintendence of the meal, as well as for conversation with his distinguished guest; and that the latter occupied what Plutarch calls a free corner, so that any messengers or other persons needing to see him could get access to him without disturbing the party.[445] The number that could be accommodated, nine, was not only a sacred and lucky one, but exactly suited for convenience of conversation and attendance.