According to the Cambridge Dictionary ('cos I don't really have a clue) :

Myrrh : "a sticky brown substance with a strong smell which is used in making perfume and incense".

Frankincense : "a thick sticky liquid that produces a sweet smell when burned and is obtained from a tree that grows in eastern Africa and Asia".

So either might be vaguely pourable. Perhaps the jug contains a spoon or brush or something to use to get it out?