One Cup or Two?
There was a man who deeply desired a son. He prayed to Saint Nicholas, asking his help that God grant him a son. The man promised to bring the son to church and together they would leave a fine gold cup on the altar in a St. Nicholas church. A son was born and when he was old enough, the man commissioned a very fine gold cup. The finished cup was so exceptional that the man could not bear to give it up. So he commissioned a second cup.
As they sailed to the Church of St. Nicholas, the boy, with the precious cup, fell into the water. Alas, he was lost, drawn down into the water and could not be found.
Filled with grief, the man continued to the church. When he came to the altar, he placed the second cup on the altar. Just as he set it down, it fell to the floor. He set it on the altar again, and, again, it fell, this time even further from the altar. A third time, he placed it on the altar; again it fell, even further than before.
People were amazed and came to see the cup. Every time it was put on the altar, it flew off, as if thrown. As they watched, the son, who had fallen into the sea, came into the church, carrying the original cup. He told how he'd fallen into the water, sinking down beneath the waves until Saint Nicholas came, keeping him from harm.
The father rejoiced and placed both golden cups on the altar. This time they stayed.
"The Life of St. Nicholas the Bishop" from The Golden Legend by Jacobus de Voragine (1275)
The Twenty Miracles of Saint Nicholas by Bernarda Bryson, Little, Brown and Company, 1960, has a nicely elaborated version of this story.