Top view of the ILMT mirror surfaced with mercury and covered with thin assembled mylar films, which prevent the formation of ripples on the surface of the mercury. A tube is attached to the aluminium beam, just to the left of the edge of the mirror, to pump the mercury to and from the mirror and the tank visible at the top left side of the mirror. Near the middle left-hand side, one can see one end of a box containing charcoal to which a black tube is attached. It is used to evacuate the vapour when the mercury has just been transferred to the mirror (see text).