In Korean culture, the hundredth day after a baby is born, you give a Paek Il, or hundred-day, party. It is supposed to be a big dinner party with lots of booze; you invite everyone you know and display your wealth.
Baby boys wear a special little outfit stamped with good luck symbols, with a funny pointy black hat that looks rather like a Chinese war helmet. Girls wear a little hanbok, a colorful dress.
Now and at the Chut Dol or Tol (first year birthday) ceremony, the baby is placed before an array of symbolic objects: money or a rice cake, meaning wealth; a piece of yarn or string, meaning long life; a book, meaning knowledge or wisdom; and a brush pen, meaning scholarly ability. The first thing the baby grabs is supposed to predict its future. At around 3 months, coincidentally, many babies are just getting the ability to reach out and grasp stuff.
At my baby's hundred-day party, we also put a computer mouse in front of him, and cleverly, he grabbed it first. Perhaps this will correctly predict the carpal tunnel he will suffer from in his future life of excessive video game playing.
The point of this party was originally to celebrate that your newborn infant was still alive, in a time when infant mortality was high. The baby is actually not supposed to leave the house until after its Paek Il.