Five years ago, Harris had an epiphany. While flicking through a copy of Lasseter's diary, which contains sketches and written accounts of his final journey, Harris opened up Google Earth on his computer screen. Beginning at Ayers Rock, as it was known in Lasseter's day, he began tracing the explorer's route, matching landmarks in the diary with geological features on the satellite mapping service.
"Every mark he put in his diary, I followed it," says Harris. "Every picture in the diary, I matched the picture on Google Earth. I drove my missus nuts once I started working it out. I'd stay up all night, miss a day's work."
It took him 12 months to pinpoint what he believed was the site of Lasseter's Reef. Since then, he and various friends have made five trips to the area, near the border of Western Australia and the Northern Territory, most recently in March.
The men are convinced they have found the reef, and they plan to head out again in the coming months. Next time, they are almost certain, they will find the elusive gold.
Many would say they are chasing a pipe dream. Neither the Australian Government nor any mining company believes there is gold beneath the sandhills. Over the decades, Lasseter's Reef has been dismissed as a fiction and the man himself as a fantasist. That has not stopped the likes of Dick Smith, the Australian businessman and adventurer, from searching for the mine.
It was while prospecting for rubies as a young man in 1897 that Lasseter got lost and, while trying to find his way, came across the fabled gold deposit. Rescued by an Afghan camel driver, he returned to the spot three years later but incorrectly recorded its location. Then, in 1930, during the Great Depression, he persuaded a group of Sydney businessmen to fund a quest for the hidden treasure.
The expedition was a disaster; Lasseter fell out with his companions, who deserted him one by one. He set off into the desert on his own, where his camels bolted, according to his diary, which was found in a cave. Left without supplies, he met a group of Aborigines who gave him food and shelter, but he died of exhaustion and malnutrition. One of his final diary entries read: "What good a reef worth millions? I would give it all for a loaf of bread."
Harris, 41, says he and his friends found a reef of the size described by Lasseter - 22.5km long - on their third trip to the desert. They have also discovered a waterhole and marker stones documented in the diary, as well as the letters "ASSE" carved into hard clay, according to Harris.
"We've not found any gold yet, but we're sure there's gold there," says Harris, who has lodged a claim over the site. "We've got no backers, it's just me and eight or nine mates, we're all just battlers. Friends and relatives have chipped in $100 here and there to help pay for expenses.
"For me, it's not so much about the money, but wanting to solve the mystery and prove that Lasseter was here, he did cross this country."
The group - armed with equipment such as ground-penetrating radar - has found geological features described by Lasseter, such as "wavy" sedimentary rocks formed by what was once an inland sea. The site is a four-hour helicopter flight from the nearest inhabited spot, the Aboriginal community of Warburton, and lies 36km off a rough track.
"We're pretty sure we're in the right area," says one of Harris' friends, Laurie Watts. "But we're still looking in a very big haystack. You're going to have to practically walk over the thing [gold] to find it."
As for the riches, Harris says: "We respect the traditional owners of the land, and we respect that it's a national legend. If we find anything, we'd look to find a way to share it with Australia.
"We're all mindful of what's happened in the past with mining companies sucking the wealth out of the country. Once my family's secure and my mates are comfortable, I'd be happy to give the rest away, whether it's helping with hospitals or paying off the national debt. I don't want to be Alan Bond or James Packer."