JERUSALEM—Israeli archaeologists have found a rare ancient toilet in Jerusalem dating back more than 2,700 years, when private bathrooms were a luxury in the holy city, authorities said Tuesday. The Israeli Antiquities Authority said the smooth, carved limestone toilet was found in a rectangular cabin that was part of a sprawling mansion overlooking what is now the Old City. It was designed for comfortable sitting, with a deep septic tank dug underneath. “A private toilet cubicle was very rare in antiquity, and only a few were found to date,” said Yaakov Billig, the director of the excavation. “Only the rich could afford toilets,” he said, adding that a famed rabbi once suggested that to be wealthy is “to have a toilet next to his table.” Animal bones and pottery found in the septic tank could shed light on the lifestyle and diet of people living at that time, as well …