A Nasik (= pandiagonal & pantriagonal) 26x26x26 magic cube does not exist. Above simple, only a pantriagonal 26x26x26 magic cube has been constructed. Theoretical it is possible to get a diagonal 26x26x26 magic cube.
Pantriagonal
[Medjig method] René Chretien used the Medjig method 3D to construct a pantriagonal 26x26x26 magic cube.
[Method of Luyendijk] I used the method of Luyendijk (for order is double odd) to construct a pantriagonal 26x26x26 magic cube.