The S&P 500 erased a 2.4% loss and finished massively 2.6% up, marking the first day since July that it has done so.
The second-to-second data on share changes provided the finest illustration of the first rush to sell, followed by a rush to purchase.
Before jumping beyond 1,900, the so-called Tick index, which contrasts the number of stocks increasing over those dropping at any one time, reached minus 1,900.
According to Bloomberg statistics going back to 1990, the market has never previously recorded such severe readings in both directions in a single day.
The Dow Jones Industrial Average, however, increased by over 1,400 points from the day's low.
The cause of the turnaround is up for debate. Some mention the necessity for options hedgers or chart support.