I will make use of another not dissimilar marvel in a like kind of work, having the concurrence of Refrigerius in doing so. Martin was prepared to throw down a pillar of immense size, on the top of which an idol stood, but there was no means by which effect could be given to his design. Well, according to his usual practice, he betakes himself to prayer. It is undoubted that then a column, to a certain degree like the other, rushed down from heaven, and falling upon the idol, it crushed to powder the whole of the seemingly indestructible mass: this would have been a small matter, had he only in an invisible way made use of the powers of heaven, but these very powers were beheld by human eyes serving Martin in a visible manner.
Again, the same Refrigerius is my witness that a woman, suffering from an issue of blood, when she had touched the garment of Martin, after the example of the woman mentioned in the Gospel, was cured in a moment of time.
A serpent, cutting its way through a river, was swimming towards the bank on which we had taken our stand. 'In the name of the Lord,' said Martin, 'I command you to return.' Instantly, at the word of the holy man, the venomous beast turned round, and while we looked on, swam across to the farther bank. As we all perceived that this had not happened without a miracle; he groaned deeply, and exclaimed, 'Serpents hear me, but men will not hear.'
Source: Dialogues (New Advent)