The remains are most likely those of Louise de Quengo, a widow of Breton nobility who died in 1656 when she was in her 60s.
The heart of her husband, Toussaint de Perrein, was found nearby, archaeologists said on Tuesday.
The body was found at a construction site for a convention centre.
Four other lead coffins dating back to the 17th century were also found in the convent, as well as 800 other graves, but they contained only skeletons, unlike the fully preserved de Quenga.
“We saw right away that there was a lot of volume, fabric, shoes,” said Rozenn Colleter, an archaeologist at the French national institute for preventive archaeological research.
Colleter also said that beneath the cape, archaeologists could distinguish “hands that were holding a crucifix”.
After two scans and an autopsy, scientists were able to discover a bit about de Quenga’s medical history.
“With Louise, we had surprise after surprise,” said Fabrice Dedouit, a radiologist and medical examiner in Toulouse.
An autopsy revealed “significant kidney stones” and “lung adhesions”, and the heart was taken out “with real surgical mastery”.
The clothes were deteriorating from years of decay but have been restored and are expected to be put on display.
Probably choosing to live out her last days at the convent, the widow was found wearing a no-frills outfit consisting of a cape, a coarse habit, a linen shirt, cork-soled shoes, woollen breeches, a shroud over her face, and several caps.
Her corpse will be reburied in Rennes in a few months.
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