The Lyell Glacier route is class 2-3.
Follow the John Muir Trail to within about a mile of Donohue Pass. Where the
trail crosses to the east side of the stream and begins a steep ascent, leave
the trail and stay to the left of the stream. Follow this side canyon up and
to the west, climbing benches and ledges on the far west end. The Lyell
Glacier will be on the right (to the south), and is broken in two large
pieces by a buttress. The west side of the glacier is hidden from view by this
buttress. Aim for the base of the buttress and cross onto the west side. Head
up to the east ridge of Mt. Lyell about a hundred yards past the buttress, or
where the angle seems smallest. Once on the east ridge, follow it to the
summit.