On June 5 or 6, depending on your time zone, millions of people around the world will see Venus inch across the sun in another occurrence of a celestial marvel that will not repeat until 2117. Because Venus is just a fraction of the sun’s width, it will appear as a tiny, black speck. Even if the weather is a washout, you can track the speck’s six-plus-hour trek from the comfort of your private base via Nasa’s live remote webcast from atop Mauna Kea in Hawaii.

Why bother bringing that up? Because of the captivating adventure angle, of course.

Rewind to 1716 when British stargazer Edmond Halley (of comet fame) urged astronomers across Europe to join him in a bid to gauge the size of our solar system by tracking the planet’s two scheduled transits across the sun. Halley would die before the transits, in 1761 and 1769, but he set prows in motion.

As historian Andrea Wulf recounts in her topical historical travelogue, Chasing Venus: The Race to Measure the Heavens, a starry cast of characters joined the mission, personally crisscrossing the ocean or dictating proceedings. Participants included quite the cast of characters, including Catherine the Great, who dispatched Russian explorers, and Charles Mason and Jeremiah Dixon, who later carved the Mason-Dixon Line across America. Other big names ranged from British explorer Captain James Cook to the captivatingly, hapless, French stargazer, Guillaume Le Gentil, who is our man.

Guillaume Le Gentil (1725-92) has to be the unluckiest explorer of all time, although no loser as the final facts spell out.

Here’s a potted guide to Le Gentil’s mostly nightmarish but finally successful enlightenment era, Venus-fixated escapades.

Fiasco One

In March 1760, the respected academic with a wanderlust left Paris bound for the French India-based colony prettily called Pondicherry. Possibly, Le Gentil should have stayed at home. The reason: the British, who were fighting the French, promptly occupied Pondicherry, making it impossible for Le Gentil to use it as his observatory.

Fiasco Two

When the day of the transit, June 6, 1761, came, the sky was clear. Unfortunately, he was stuck in his bucking boat and so could not make astronomical observations. “Zut alors!”

Fiasco Three

After travelling so far, Le Gentil made what, on the surface seemed, a wise decision. He decided to wait for the next Venus transit, due in another eight years.

And you thought waiting 20 minutes for a train was boring.

When that time came, Pondicherry was back in French hands. So seeing the second, 1769 transit seemed doable – all the more so because the mornings in the previous month had been lovely. However, on the fateful day, the sky clouded over. Poor Le Gentil saw nothing. The disaster pushed him to insanity’s edge.

Fiasco Four

Le Gentil recovered the strength to return to his homeland.

Of course, the return trip was smooth sailing… not.

First, the trip was held up by dysentery, an intestinal infection causing severe diarrhea with the presence of blood and mucus in the feces. Then, Le Gentil’s ship was caught in a storm and dropped him off at what was known then as the island of Ile Bourbon (now, the island of Reunion), where he was forced to wait until a Spanish ship picked him up.

Fiasco Five

After some epic meandering, Le Gentil finally reached Paris in 1771. There, he had a joyous reunion with his family… right?

No reunion was in the cards for the jinxed Le Gentil.

Le Gentil found that he had been declared legally dead and been replaced in the Royal Academy of Sciences. Worse, his wife had remarried. Worse still, all his relatives had “gleefully plundered his estate.”

Redemption

It took long litigation and the king’s intervention before wrongs were rectified. Le Gentil got back his seat in the academy, remarried and lived happily for another 21 years. So, a happy ending, after all.

Either way, you must admire Le Gentil’s tenacity. The first fiasco alone would have paralyzed many would-be explorers.