When Black Jack Randall is flogging Jamie, blood appears and then disappears on his sleeves as the flogging progresses.
Brigadier General Lord Thomas states Claire has had a mesmerizing experience. The term "mesmerizing" was not yet coined as Frank Mesmer was born in 1734 and would not have been experimenting in 1743.
The black hole of Calcutta is mentioned. However, that event happened in 1756, 13 years after this scene.