Letters Sir Edmund Hillary wrote to his family are up for auction next week, with one written on the eve of his historic Mt Everest ascent reveals a man facing the possibility of his own death.
Cordy's Auctions' Ross Millar said of the letters, "When I transcribed this one from the 20th of May, nine days before Hillary and Tenzing summited Everest, I thought, 'Wow.'"
In a letter written to his brother Rexford, the soon-to-be famous beekeeper, spoke about his experimental oxygen equipment, and asked for their mother to be looked after in the event of his death.
"Our oxygen gear is still pretty experimental ... In the unfortunate business of anything going wrong ... That mother should be looked after," it read.
Hillary's nephew, John Hillary, said, "Both the boys were very close to their mother. Oh, we're all mumma boys at heart, yes".
John is selling eight of his unce's letters, which he inherited from his father Rexford, at an auction.
Also up on the auction block is a necklace mounted with a stone from the top of Mt Everest.
The Government intervened to stop the sale of Sir Edmund's watches by his widow June in 2010, but isn't making a commitment to acquire the letters.
Prime Minister Jacinda Ardern said of the auction, "They are still matters for the family".
"It's difficult exactly where the interest will lie. Will it come from people who are Everest afficianados who are crazy? We've only put $30- to $60,000 on it," Mr Millar said.
John's keeping alive the family beekeeping tradition, and while he feels guilty about letting history go for financial reasons, he believes memories are more important.
"For me, Ed is something different to me than he is to you guys, OK? He's an uncle who I grew up around my entire life," John said.
"He was a really, really good uncle."
The Hillary family said it understands the circumstances surrounding the sale, scheduled for the end of the month.