It was by EL Ames, three English and the guides JJ Inseng, F Andenmatten and three other guides on August 26th, 1856.
Please see GETTING THERE section in the MAIN PAGE.
As "The Alpine 4000 m Peaks by the Classic Routes" by Richard Goedeke says: "From Weissmeshütte go NE over grassy ridges and a ramp to the glacier stream. Ascend the path on the left (North) of this on moraine ridges (with steep, short bends near the top) to the beginning of the prominent ridge wich divides Holaubgletscher (S) from Lagginhorngletscher (N). Ascend on the left over moraine debris and snow, pass South of the tongue of the Lagginhorn Glacier and then go up over the glacier to its northern upper end. From there move left (West) to a big block terrace (2 hours). To reach this point from the Hohsaas cableway station: head North-East, descending somewhat to the Hohlaubgletscher. Traverse under the tongue, following little side of the glacier. There, ascend obliquely left over a slabby ramp (little cairns, pitches of II), then traverse and finally climb again to the ridge between Holaubgletscher and Lagginhorngletscher. Move to the other side until almost level with the Lagginhorngletscher and continue as previously described to the block terrace (1 hour)".
"From the block terrace head North-Eastwards, following the picturesque cairns to the ridge (wich can also be climbed direct, without reference to the glaciers). Follow the crampon scratches and path on the Southern flank (various possibilities) moving steadly upwards in the direction of the mountain. Finally go directly along th crest, with a touch of exposure on the view down to the Fletschhorngletscher. Continue (pitch of II) the ridge. Climb debris and rock. Avoid the snow-field by traversing right as low as possible and thence go up to the summit block. Continue, keeping near the edge on the right to finally make a surprisingly airy finish to gain the highest point".
Necessary gear for a rock and glacier ascent in the Alps: crampons, axe, helmet (stone-fall in the upper part) and rope (optional).