New Zealand Alpine Club general manager Sam Newton said the only other winter climb, 24 years ago by a party of four, took two days.
"It's an incredible climb - an incredible feat of talent and endurance," Mr Newton said.
Not content with that, McKinnon then descended from Popes Nose to the Upper Volta Glacier to the north for an assault on the northeast face of nearby Mt Aspiring.
But that climb was thwarted by poor conditions and the weather was packing in so McKinnon, aged in his late 30s, battled across the Bonar Glacier in gale-force winds and a whiteout to reach the sanctuary of French Ridge Hut - which he had passed on his trek to Popes Nose.
The reclusive climber could not be reached last night, but in an earlier statement said: "The unfolding of this attempt was long and arduous beyond words and required mental effort and determination in excess of anything previously required of me."
McKinnon, who in 2010 became the first person to make solo ascents of all 34 of New Zealand's 3000m-plus mountains, last year succeeded in scaling the west face of 2723m Mt Tutoko - long regarded as one of the country's last great challenges.
- additional reporting: Martin Johnston