After the longest reign since Augustus ( surpassing Tiberius by a couple of months ) , Antoninus died of fever about twelve miles ( 19 km ) from Rome , on 7 March 161 . The last word that he uttered when the tribune of the night-watch came to ask the password was `` aequanimitas '' ( equanimity ) . After the longest reign since Augustus ( surpassing Tiberius by a couple of months ) , Antoninus died of fever at Lorium in Etruria , about twelve miles ( 19 km ) from Rome , on 7 March 161 , giving the keynote to his life in the last word that he uttered when the tribune of the night-watch came to ask the passwordâ '' `` aequanimitas '' ( equanimity ) .