Steve Gurney and Steve Moffatt are following in the footsteps of two pioneering mountaineers.
Gurney, a former Coast-to-Coast champion, and Moffatt, a triathlon and endurance athlete, are re-enacting the unsuccessful 1890 expedition by Marmaduke Dixon and George Mannering to be the first to reach the summit of Aoraki-Mt Cook.
The challenge began on Thursday and should be completed by Saturday.
It shadows the route taken by Dixon and Mannering from Christchurch to near the summit of Aoraki-Mt Cook, then east to Oamaru.
Gurney is using modern technology and equipment, and Moffatt is using only what was available in 1890.
Gurney began his travels by train while Moffatt set off on horseback.
They both will kayak down the Pukaki and Waitaki Rivers to the North Otago coast.