"Tre giorni son che Nina in letto senesta" (often called "Nina" or the "Siciliana") is an 18th Century song traditionally attributed to Pergolesi, but now more often to Vincenzo Ciampi (1719–1762).
The song was one of the "Arie antiche" favourites of 19th Century salons associated with Alessandro Parisotti, and in the 20th Century was recorded by Enrico Caruso, Richard Tucker as well as more recently, attributed to Ciampi, by Alfredo Kraus and Ramon Vargas.
The attribution to Pergolesi may have come from the mistaken assumption that the song is based on an aria sung about Nina in Pergolesi's Lo frate 'nnamorato. (from Wikkipedia)
The sung version is