The Portuguese slave ship had left Mozambique Island four weeks earlier and headed along the East African coast with its cargo of 500 captives, bound for the rice and cotton plantations of northern Brazil.
Now, two days after Christmas in 1794, the São José Paquete de Africa had been blown into treacherous waters near the Dutch settlement of Cape Town in southern Africa, and was impaled on rocks.
It was 2am. And as the ship, weighed down with cast iron ballast bars and human beings, was torn apart in the swells, the captain, crew and many slaves reached shore with a rescue line.
But 212 slaves drowned in the frigid water, their bodies probably washing up on shore later. Eleven more died in the next few days.
Today, four of those ballast bars - sacred relics of the slave trade, as one historian put it - arrived at a storage site in Maryland for the Smithsonian's new National Museum of African American History and Culture.
Oblong in shape, they were dark brown and chipped with age. Each weighed 40kg, perhaps the weight of some of the slaves on board.
"These blocks were with the slaves," said Jaco Boshoff, the South African marine archaeologist from Cape Town's Iziko Museums who brought them to the surface.
"Although we haven't found human remains - [and] there's an expectation that we might do that - we will find them trapped under something like a ballast block," he said.
The bars constitute some of the remnants from the first known slave ship to sink with Africans on board that has been identified, studied and excavated, the Smithsonian said.
A wooden pulley block from the ship's rigging and a piece of mangrove timber from the São José's hull will be delivered later.
They are modest but haunting reminders of the 400-year global commerce in slaves that transformed 12.5 million Africans into a commodity and shipped them like cargo to the Western Hemisphere in bondage.
Tens of thousands of men, women and children died on ships like the São José during the "Middle Passage" across the ocean.
The artifacts will be displayed in the new museum - set to open on the National Mall on September 24 - with hundreds of other objects that tell the story of African Americans.
The remnants recall the beginning of the slave ship saga.
They are on a 10-year loan from the Iziko Museums, near where the wreck was discovered.
"I spent years looking around the world trying to find slave ship pieces . . . as almost like a religious relic," said Lonnie Bunch III, the museum's founding director. They "are really the only tangible evidence that these people existed."
The wreck of the São José was discovered in the 1980s in about 9m of water, 120m off shore, near the community of Clifton, according to experts at the Smithsonian, George Washington University and the international Slave Wrecks Project.
But it was long thought to be an older Dutch vessel. And it was not until 2010-11 that maritime archaeologists in South Africa found the captain's account of the sinking in local archives, as well as the telltale ballast bars on the bottom.
When researchers in Portugal found the São José's manifest, the document said the ship had originally sailed from Lisbon with more than 1000 iron ballast bars, said Stephen Lubkemann, an associate professor at George Washington University, who is part of the Slave Wrecks Project.
Such ballast was often used on slave ships to compensate for the relatively light weight of human cargo.
LIFE ON A SLAVE SHIP
Many "slavers" were distinguished by netting that was stretched out from the hull to catch slaves who jumped overboard, and a deck barricade built to guard against uprisings.
A slave ship could hold as few as 30 captives or as many as 700, according to historian Marcus Rediker's study of the vessels.
The São José had headed to East Africa for its cargo because British anti-slaving patrols were trying to suppress the traditional trade from West Africa.
Typically, a slave ship would sail to Africa from a home port such as Lisbon, or Liverpool in Britain, or a city on the East Coast of the United States.
The ship would linger off the African coast, often for months, until it was "slaved," or filled up. It would then take its cargo to South America, the Caribbean or the United States for sale.
Slaves were jammed on board and given a number. Sometimes they were branded.
"When stowed, there was not room to put down the point of stick between one and another," one crewman recalled later, Rediker said.
Disease, death and cruelty were constants.
The hold below decks, where slaves were packed, came "nearer to the resemblance of a slaughterhouse than anything I can compare it to," a British doctor reported.
Mortality rates were high. The dead were thrown into the sea, and sharks grew accustomed to following the ships.
Slaves resisted however they could, although they often were shackled or chained.
Many jumped overboard to try to escape or commit suicide. Some refused to eat. But slave ships had a cruel device called the speculum oris that was used to wedge open the mouth for force-feeding.
Slaves revolted often. The Liverpool slave ship, Unity, had four insurrections in one voyage, Rediker found. In such cases, the crew would retreat behind the deck barricade and fire on the slaves with muskets and deck guns loaded with grape shot.