Rather than an essence as in almond, rose or vanilla essence, this is a cologne used in rituals. I think you would find it difficult to get dictionary or scholarly references to it. I am very familiar with the use of Esencia de Pompeya in the Caribbean, and by some Latin American ritualists in the USA. In the USA it has also been translated as "Pompeii cologne" or "Pompeii perfume" by some distributors and users. IO prefer cologne because it is more of a cologne than a perfume to me.
See e.g. the mention in the following treatise: http://www.scribd.com/doc/9610198/urantia
See also: http://www.neworleansmistic.com/powders/haitian.htm

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Note added at 1 hr (2009-06-02 20:36:31 GMT)
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Although I think it is a cologne rather than a perfume you may have to decide which one is best, depending on your audience. I imagine that "perfume" conveys more of an aura of ritual and ceremony to some than does "cologne".