The wick of the candle represents the physical world. The blue flame nearest to the wick is the first spiritual world above our physical one, of the Sefirah of Malchut – Rulership. Above it is the flame in the shape of a letter vav, or a straight vertical line. The numerical value of vav is 6, and it corresponds to the next six Sefirot, that is, Kindness, Strength, Beauty, Victory, Splendor, and Foundation. Next is the hottest white flame, which corresponds to the Sefirah of Understanding.
Then comes the light radiating from the candle, and this is the power to perceive, or Wisdom. Finally, there is the concept of the flame itself, and this corresponds to the highest Sefirah, the Crown, or Will.
All of these parts are united only through a wick. By contemplating a flame in this manner, one can bind himself to the Ten Sefirot.
The word used for the candle in the Sefer Yetzirah here is “gachelet,” or coal, and its numerical value is 441. The numerical value of the word Truth, “Emet” is the same. It is Truth that binds all opposites together. This is indicated in the word itself, for letter Aleph of Emet is the first letter of the alphabet, and letter Tav of Emet is the last letter of the alphabet. This is also the concept that the highest and the lowest meet and flow into each other. That infinite chain of transformations can also be used as a mental exercise, or meditation.