Illustrated Companion to the Latin Dictionary/Sigma

This article incorporates text from a publication now in the public domain: Rich, Anthony (1849). The illustrated companion to the Latin dictionary, and Greek lexicon. p. vi. OCLC 894670115. https://archive.org/details/illustratedcompa00rich. 

SIG'MA. A semicircular dining-couch (Mart. xiv. 87. Apul. Met. v. p. 90. suggestum semirotundum), adapted for use with a round table (orbis); and so named because it resembled one of the early forms of the Greek letter Sigma, which was written like our C. It was not invented until the square dining-table (quadra) fell into disuse, when the introduction of the circular form necessitated a similar change in the shape of the sofa used with it. But it was more convenient than the old lectus tricliniaris, because it did not like that require the fixed number of nine guests, but could be arranged for smaller parties; for six (Mart. ix. 60.), seven (Id. x. 48.) or eight (Lamprid. Elag. 25.); and the order of precedence in the places upon it ran straight on in regular succession, from the highest to the lowest.

2. A circular seat round the bottom of the hot-water bath, on which the bathers sat and washed themselves. (Sidon. Ep. ii. 2.) Also the bath itself. Id. ib.