Read this excerpt from The First Men in the Moon. There came a little je, a noise like champagne being uncorked in another room, and a faint whistling sound. For just one instant I had a sense of enormous tension, a transient conviction that my feet were pressing downward with a force of countless tons. It lasted for an infinitesimal time.
What is the meaning of the italicized word, transient, as it is used above?

passing
strong
religious
heavy