In the celebration of the Extraordinary Form of the Roman Rite, the minister (deacon or altar server) is directed to raise the chasuble slightly in his left hand as the celebrant elevates the Sacred Host and then the Chalice. This direction is given in the Ritus Servandus VIII,8; the Caeremoniale Episcoporum II, viii and a decision of the Congregation of Sacred Rites no 3535.
What is the origin of this practice? It dates from that period when chasubles were voluminous and constrained the celebrant from raising his arms above his head. Lifting the lower right hand corner of the chasuble actually enables the celebrant a greater movement of the arms. Thus, the origin of this ceremonial action is purely practical. Much has been written about mystic and symbolic meanings as being the origin of this action, all of which is complete nonsense.
The ceremonial books direct that the raising of the chasuble be a very subtle action. It was never intended that the chasuble be raised half-way up the celebrant's back or - worse still - be held up by both hands of the minister, making the chasuble seem like some fantastical ecclesiastical sail. Most assuredly such exaggerated movements are distracting both to the celebrant and to the congregation.
If the chasuble is not very ample at all, there is even more reason for its raising at the Elevation to be a very modest action: just a couple of inches at most. Furthermore, this gesture only accompanies the actual Elevations, and not the celebrant's accompanying genuflections.
Attached is a beautiful photograph of a Low Mass celebrated at Prinknash Abbey (UK) in 1940, illustrating perfectly how it should be done.