Today, simply attempting it won't be enough for Phelps and Hoff. Before it's over, there will be two new records and two new gold medals. Phelps will be within an arm's reach of the most venerable record on the books - Mark Spitz's mark of seven gold medals at a single Games - and Hoff an arm's length or two away from a couple of more medals.
9:10: After stretching, both swimmers can be spotted in the warm-up pool. Swimming the entire length of the pool repeatedly for more than a half-hour each, they only occasionally stop at the wall for a quick breather.
9:30: Time for the dressing room. As fast as he is in the water, it takes Phelps about five minutes to put on a pair of pants. Hoff is wearing the full-body suit for her first race, which means she needs about 15 minutes. It takes so long because slipping into the space-age suit is kind of like putting on a Fruit Roll-up.
9:45: Both athletes are back in the warm-up pool for about 15 more minutes. They'll spend the day in and out of the pool, and each will log about five miles in the water through the course of the day. About 15 minutes before the start of their respective races, they're shuffled off to the ready-room.
10:13: While Phelps sits in solitude, his iPod providing the only company, Hoff is already on the starting blocks, waiting for a buzzer to signal the start of the 200-meter freestyle, a race in which she has twice set the American record.
1:55.78 later: Hoff finishes a disappointing fourth, 0.73 of a second away from a medal. Her time is still good for an American record.
10:16: As Hoff exits the pool to the right, Phelps approaches from the left. He's set for his first race of the day, the 200 butterfly, a race in which he has set the world record six times.
1:52.03 later: Make that seven times. Not just Phelps' fourth gold medal, but his fourth world record here.
10:25: Phelps follows Hoff's footsteps out of the pool. He has about 55 minutes until his next race. The post-race routine isn't simple. Normally, athletes weave through a gated corridor, where reporters from television stations, wire services and newspapers are lined up. After brief interviews, they head to get tested for doping, staying as long as it takes to get a sample. Because each has another race, there's no time for that now, and doping will wait until after the day's final race. For now, each heads right back in the water for a warm-down swim.
Swimmers are encouraged to reach the pool within three minutes of completing a race. When they arrive, pricks to the ears checks the levels of lactic acid in their bodies. They hit the water and can't leave the pool area until another test reveals lactic acid levels have returned to a comfortable level. For some swimmers, this could take 15 to 20 minutes or more. For Phelps - another of his physical oddities - he can often be ready in 10 minutes or less.
This is a crucial part of the day. At the Olympics, it might not be as urgent for most swimmers to rejuvenate quickly. But Phelps is racing in eight events and Hoff in six. And each still has another in this session.
"It's the kind of thing you can get by with for a couple of days," says Bob Bowman, his coach. "But by the time you get to Day 8 or 9, it's a lot harder."
10:45: Time for a costume change. Both are switching suits, which takes about 15 minutes apiece. Phelps will wear the full-body suit for the 800 freestyle relay.
11:02: Phelps takes his familiar spot atop the highest platform in the medal ceremony. Afterward, he tosses flowers to his mother.
All the while, Hoff prepares for her next race in the ready room. All swimmers are required to check into the room 15 minutes before the start of each race. The room is sparse, with a handful of volunteers, rows of white chairs and a television at one end.
Her second race of the day just minutes away, Hoff is about to show just what it means to compete in two finals in a single day.
Before Phelps, a program including such "doubles" was almost unheard of. "Physiologically, [Phelps] has obviously trained his body to do it," Bowman says. "But it's mainly mental."
11:15: Phelps is back in the ready room and Hoff is back on the blocks, this time for the 200 individual medley. She's set the American record five times .
2:10.68 later: Hoff is again fourth, posting a time nearly a full second slower than she had at the Olympic trials.
11:21: Before the 800 freestyle relay, Phelps and his four teammates are introduced the crowd. Phelps still has earbuds in his ears, his heartbeat no match for the boom of hip-hop bass. He's first on the blocks and first to hit each wall. The Americans have an incredible 2.64 second lead after Phelps' leg.
6:58.56 later: Another race, another record, another gold. The U.S. finishes 5.14 seconds ahead of any other country, completing yet another historic night for Phelps and leaving him just two medals shy of tying Spitz.
11:50: The crowd waits to see Phelps resume his familiar post on the medal stand. The national anthem plays and Phelps - with more gold than Midas - smiles.
He's happy, relieved and tired. But he still has to visit doping and attend a news conference. A team meeting and an evening session at the pool still await. As does the possibility of three more medals and a special place in history. It's an amazing thing to witness.
Not that Phelps has any time to catch his breath and soak any of it in.