On Oct. 9, Austrian skydiver Felix Baumgartner will jump from an air balloon floating 120,000 feet above Earth in an attempt to be the first human to break the speed of sound in free fall. After leaping from the capsule, the 43-year-old adventurer hopes to reach 690 mph, or Mach 1. If successful, Baumgartner will be immortalized in the record books for highest skydive, fastest free fall, longest free fall and highest manned balloon flight.

A 23-mile plummet toward Earth with little more than a full-pressure suit, helmet and parachute. Why?!

Ever since the earliest adrenaline junkies have been performing their feats of derring-do, stuntmen and daredevils have been testing the limits of safety (and sanity) in the name of seeking thrills. If Baumgartner succeeds in his efforts, his name will certainly be added to the ranks of the world's most death-defying acts. Here are some of the most memorable to date:

1. High wire walk between the Twin Towers At 110 floors above bustling lower Manhattan, French high wire artist Philippe Petit (pictured above) walked back and forth for nearly 45 minutes with nothing more than a balancing pole. The 1974 stunt extraordinaire is the subject of the fascinating documentary, "Man on Wire." The walk in the sky was so well-received by the public that all formal charges were dropped, and Petit was presented with a lifetime pass to the Twin Towers' Observation Deck by the Port Authority of New York and New Jersey.

2. Escape from a secured and submerged crate We think of Harry Houdini as a magician, but he was clearly a magician with daredevil tendencies. One of Houdini's most famous tricks was his escape from a securely closed packing crate after it had been dropped into water. Houdini first performed the escape in New York's East River in 1912. Locked in handcuffs and leg-irons, the crate he was in was then nailed shut and secured and weighted with 200 pounds of lead. The crate was lowered into the water; Houdini escaped in 57 seconds. We can't tell you how he did it (magician's code of honor and such) but every time the trick was performed, the magician appears to have run the distinct risk of drowning.

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