The first drop took eight years. No one saw the three drips that fell before Mr. Mainstone began his vigil in 1961, and the unlucky researcher has missed all five that have happened since then.

In 1979, Mr. Mainstone was so sure the drop was about to fall that he stayed at his office all day one Saturday by its side. Exhausted, he decided to rest on Sunday, only to find early Monday morning that the pitch had dropped in his absence.

In 1988, while the experiment was displayed at the World Expo in Brisbane, the professor stepped away from the experiment for about five minutes to grab a beverage. He returned to find the drop had fallen.

Frustrated by repeated near misses, he pointed a webcam at the droplet in the 1990s. He was at a conference in London when a colleague sent an email reporting the drop might soon fall. He told them not to worry—the camera would capture it all. But a power outage may have caused the camera to fail, and that drop, the most recent, went unobserved as well.