IN THE spring of 1976 Mau Piailug offered to sail a boat from Hawaii to Tahiti. The expedition, covering 2,500 miles, was organised by the Polynesian Voyaging Society to see if ancient seafarers could have gone that way, through open ocean. The boat was beautiful, a double-hulled canoe named Hokule'a, or “Star of Gladness” (Arcturus to Western science). But there was no one to captain her. At that time, Mau was the only man who knew the ancient Polynesian art of sailing by the stars, the feel of the wind and the look of the sea. So he stepped forward.

As a Micronesian he did not know the waters or the winds round Tahiti, far south-east. But he had an image of Tahiti in his head. He knew that if he aimed for that image, he would not get lost. And he never did. More than 2,000 miles out, a flock of small white terns skimmed past the Hokule'a heading for the still invisible Mataiva Atoll, next to Tahiti. Mau knew then that the voyage was almost over.

On that month-long trip he carried no compass, sextant or charts. He was not against modern instruments on principle. A compass could occasionally be useful in daylight; and, at least in old age, he wore a chunky watch. But Mau did not operate on latitude, longitude, angles, or mathematical calculations of any kind. He walked, and sailed, under an arching web of stars moving slowly east to west from their rising to their setting points, and knew them so well—more than 100 of them by name, and their associated stars by colour, light and habit—that he seemed to hold a whole cosmos in his head, with himself, determined, stocky and unassuming, at the nub of the celestial action.

Sharing breadfruit

Setting out on an ocean voyage, with water in gourds and pounded tubers tied up in leaves, he would point his canoe into the right slant of wind, and then along a path between a rising star and an opposite, setting one. With his departure star astern and his destination star ahead, he could keep to his course. By day he was guided by the rising and setting sun but also by the ocean herself, the mother of life. He could read how far he was from shore, and its direction, by the feel of the swell against the hull. He could detect shallower water by colour, and see the light of invisible lagoons reflected in the undersides of clouds. Sweeter-tasting fish meant rivers in the offing; groups of birds, homing in the evening, showed him where land lay.

He began to learn all this as a baby, when his grandfather, himself a master navigator, held his tiny body in tidal pools to teach him how waves and wind blew differently from place to place. Later came intensive memorising of the star-compass, a circle of coral pebbles, each pebble a star, laid out in the sand round a palm-frond boat. This was not dilettantism, but essential study; on tiny Satawal Atoll, where he spent his life, deep-sea fishing out in the Pacific was necessary to survive.

Nonetheless, the old ways were changing fast. After Mau, at 18, was made a palu or initiated navigator, hung with garlands and showered with yellow turmeric to show the knowledge he had gained, no other Pacific islander was initiated for 39 years. Alone, he went out in his boat with the proper incantations to the spirits of the ocean, with proper “magical protection” against the evil octopus that lurked in the waters between Pafang and Chuuk, and with the wisdom never to get lost—or only once, when he was wrecked by a typhoon and spent seven months, with his crew, waiting to be rescued from an uninhabited island.

As a palu, however, he could not allow his skills to die with him. He was duty-bound to pass them on. Hence his agreement to captain the Hokule'a. That voyage, which proved that the migration of peoples from the south and west to Hawaii was not accident, but probably a deliberate act of superlative sea- and starcraft, transformed the self-image of Hawaiians; and it changed Mau's life. Suddenly, he was in demand as a teacher. Patiently, pointer in hand, one leg tucked under him, he would explain the star compass to new would-be navigators; but he allowed them to write it down. He knew they could never keep it all in their heads, as he had.

Much of what he knew, of course, was secret. The secrecy was serious: when he spoke of spirits, his smiling face became deadly sober and even scared. To a very few students, he passed on “The Talk of the Sea” and “The Talk of the Light”. By doing so, he broke a rule that Micronesian knowledge should remain in those islands only. It seemed to him, though, that Polynesians and Micronesians were one people, united by the vast ocean which he, and they, had crisscrossed for millennia in their tiny boats.

In 2007 the people of Hawaii gave him a present of a double-hulled canoe, the Alingano Maisu. Maisu means “ripe breadfruit blown from a tree in a storm”, which anyone may eat. The breadfruit was Mau's favourite tree anyway: tall and light, with a twisty grain excellent for boat-building, sticky latex for caulking, and big starchy fruit which, fermented, made the ideal food for an ocean voyage. But maisu also referred to easy, communal sharing of something good: like the knowledge of how to sail for weeks out on the Pacific, without maps, going by the stars.