In the case of the transit of Mercury in 1631 , Kepler had been extremely uncertain of the parameters for Mercury .
In the case of the transit of Mercury in 1631 , Kepler advised observers to look for the transit the day before and after the predicted date .
In the case of the transit of Mercury in 1631 , Kepler had been extremely uncertain of the parameters for Mercury , and advised observers to look for the transit the day before and after the predicted date .