I was intrigued by the lines in Wuthering Heights which show Catherine's mystical connection to Heathcliff. Her lines, "Whatever our souls are made of, his and mine are the same . . . " really touched a nerve in me. This sounded exactly like the description in Huna of twin souls and I wondered where this 19th century author came up with the idea. So, I did a bit of research.
I found that Emily Bronte was most likely influenced by the poem "Epipsychidion" by Percy Shelley, the early 19th century poet. The title translates to "the soul outside the soul," and explores the Romantic notion of union in death. Here's an excerpt:
We shall become the same, we shall be one . . .
In one another's substance finding food,
Like flames too pure and light and unimbued
To nourish their bright lives with baser prey,
Which point to Heaven and cannot pass away:
One hope within two wills, one will beneath
Two overshadowing minds, one life, one death,
One Heaven, one Hell, one immortality,
And one annihilation. . . .
Makes you want to swoon, doesn't it?