Ian McKellan, left, as Gandalf and Elijah Wood as Frodo in 'The Lord of the Rings.' (Pierre Vinet/New Line Cinema)

Ian McKellan, left, as Gandalf and Elijah Wood as Frodo in 'The Lord of the Rings.' (Pierre Vinet/New Line Cinema)

In the old days, when a passage in a book really stuck with you, you'd get out a yellow magic marker or something similar and highlight it.

Today, many people who own an Amazon Kindle book reader use its highlighting function to note remarkable bits of writing that interest or inspire them.

And now, we know which of those passages are the most popular with millions of users of the e-reader.

The Atlantic got its hands on data from Amazon that reveal the most popular highlighted passages from Kindle's most popular books. Here's a sampling:

The most-highlighted passage from The Lord of the Rings:

"The wide world is all about you: you can fence yourselves in, but you cannot for ever fence it out."

From Harry Potter and the Order of the Phoenix:

"Just because you've got the emotional range of a teaspoon doesn't mean we all have."

See what other literary snippets Kindle readers like.