 On 3 December 1846 , Brunner began what became his longest and most arduous expedition . He planned to follow the Buller River to the sea and then trek down the West Coast as far south as Milford Sound . During his previous expedition , he had been told of the existence of a route through the Southern Alps by the Māori at the Arahura River . He hoped to discover this route and use it to cross the Southern Alps and reach Canterbury . He was accompanied once again by Kehu , who brought along his wife . Another Māori , Pitewate , a friend of Kehu 's , also joined the venture , accompanied by his wife . Brunner provided clothing and shoes for his companions . The wives proved problematic during the journey as they quarrelled , sometimes supported by their husbands , and Brunner would have to mediate . 
