Complex sentence: The oft-repeated tale of Messalina's all-night sex competition with a prostitute comes from Book X of Pliny the Elder's "Natural History", according to which the competition lasted for 24 hours and Messalina won with a score of 25 partners.
Split into simpler sentences: The oft-repeated tale of Messalina's all-night sex competition with a prostitute comes from Book X of Pliny the Elder's "Natural History". According to Pliny, the competition lasted for 24 hours and Messalina won with a score of 25 partners.