Ignatius of Loyola was accessible to every one, but would speak on none but spiritual subjects. He preached for two or three hours together on three days in the week, besides Sundays and holidays; nor did he desist even when his strength was much reduced by continual low-fever. The crowds at length became so great, that he was forced to leave Azpeytia for the open country, men climbing up into the trees to hear him;
and so marvellously was he assisted by the power of God, that he was distinctly heard at a distance of three hundred yards, although his voice was not naturally strong.
He spoke entirely from the impulse of the moment, preparing nothing beforehand, but throwing his whole soul into his discourses, which, therefore, in spite of their extreme simplicity, produced extraordinary effects.
Link (here) to Stewart Rose. his book is entitled Ignatius of Loyola and the early Jesuits.