They threw the bottle in 1886 and opened it in 2018

On 12 June 1886, the captain of the German barque Paula wrote his ship's position by hand on a printed form, rolled it up, pushed it into a Dutch gin bottle and threw it overboard in the middle of the Indian Ocean. Nobody touched that paper again until 21 January 2018, a hundred and thirty-one years later and on the other side of the world.

He did it because it was part of his job. Since 1864 there had been a drift experiment running that asked German merchant captains to drop numbered bottles along known routes, in order to map how the ocean currents moved. The address printed on the paper was that of the naval observatory in Hamburg, which from 1875 was called the Deutsche Seewarte and took the programme over. The form had boxes to fill in: date, latitude, longitude, ship's name, port of registry. And an instruction printed in several languages for whoever found it: note down where and when it turned up, and return the paper to the observatory in Hamburg or to the nearest German consulate.

The experiment ran for sixty-nine years and was shut down in 1933. Thousands of bottles went into the water and 662 forms came back. The Paula's was not among them, and nobody claimed it while any of the people who had handled it was still alive.

That January morning, Tonya Illman was walking through the dunes of Wedge Island, about 180 kilometres north of Perth, on the Western Australian coast. She saw a glass neck sticking out of the sand and picked the bottle up, thinking it would look good on a shelf. When she tipped it over, a roll of paper tied with string fell out, damp and packed tight from so many years rolled up. At home they dried it for a while in a low oven so they could unroll it without breaking it. It was the form, with the date written by hand and the ink still readable.

The checking was done by the Western Australian Museum, in Fremantle. Ross Anderson, its maritime archaeology curator, asked the German and Dutch naval and meteorological archives for help. The Paula's logbook, kept in Germany, had an entry for 12 June 1886 recording the release of a bottle at that exact position. The handwriting in the logbook and the handwriting on the form were the same hand. The form's printed serial number matched the programme's series as well.

Guinness certified it as the oldest message in a bottle ever recovered: 131 years and 223 days between the throw and the find. The previous record was 108 years and 138 days, and it belonged to a different bottle from a different experiment: the Marine Biological Association of Plymouth released it in 1906, and it turned up in 2015 on the German island of Amrum. The Paula's took twenty-three years off it in one go.

The researchers who studied the state of the paper and the behaviour of the local currents worked out how long the bottle had spent in the water. Most likely it reached that beach in under twelve months, carried in by the Leeuwin Current, and stayed buried in the dune until Tonya Illman stubbed her foot on the glass neck. The voyage lasted a year. The other hundred and thirty it spent in that dune, on dry land, within reach of anyone who had dug down a hand's depth.