A small stage is partitioned off by dark curtains. In the middle of the stage appears the floating head of a young woman (since the name of the illusion is "Stella". Substitute a man and a man's name if desired!). She is alive and talks; probably complains about the frilly collar she is wearing (or the scarf, or whatever). When the performer deems it time, he has her blow out a candle and takes it away around the side of the curtains. He informs the audience he's going to open up a small panel below the woman's head to show that she has no body; he does so and under her appears a candle on a table — the same candle that she blew out. Then the curtains close and everyone is content.
There is nothing complicated at all about this. The two diagonal lines inside the curtains are two golden rods or ropes or some other construction which hides the sides of a mirror, which goes from the front of the stage, at the bottom, to the back, behind and higher than the woman's head. There is a hole in the mirror, large enough for her or him to get her/his head through; s/he must wear some sort of collar that will hide the hole. The table and the candle are actually fixed to the top of the stage, behind the droopy top curtain: the table is vertical and the candle is fixed to it horizontally. To make it appear as if the table suddenly appears some inconspicuous drop-curtain arrangement is required.
It's all a matter of angles and lights. The entire scene is well illuminated, care being taken of course to hide any reflections. The ceiling of the stage and its floor as well as the sides are of identical colour and texture.
This is much the same illusion as the "decapitated Princess".