How did Harry remove the Philosopher's Stone from the Mirror of Erised?

‘How did I get the Stone out of the Mirror?’

‘Ah, now, I’m glad you asked me that. It was one of my more brilliant ideas, and between you and me, that’s saying something. You see, only one who wanted to find the Stone – find it, but not use it – would be able to get it, otherwise they’d just see themselves making gold or drinking Elixir of Life.’

_{Philosopher's Stone - page 217 - Bloomsbury - chapter seventeen, The Man With Two Faces - Harry talking with Dumbledore}

Dumbledore doesn't directly answer Harry's question, but rather describes under what circumstances a person could collect the Philosopher's Stone from the mirror. Did Harry have to do anything to retrieve the stone, such as reach into the mirror and take it? If not, what kind of magic could have removed the stone from the mirror and put it into Harry's possession?

A canon-based answer is preferred, such as the books, interviews with J.K. Rowling, or info from Pottermore, but subjective answers within the spirit of canon are welcome.

Answer

The books are very clear on the subject of how the stone came into his possession...

He saw his reflection, pale and scared-looking at first. But a moment later, the reflection smiled at him. It put its hand into its pocket and pulled out a blood-red stone. It winked and put the Stone back in its pocket – and as it did so, Harry felt something heavy drop into his real pocket. Somehow – incredibly – he’d got the Stone._{^{HPatPS - The Man with Two Faces}}

...but completely lacking in any real explanation of what spells or enchantments allowed this to happen.

There's a little more info on Pottermore about the Mirror (as hiding place) but nothing useful, other than that Dumbledore has made modifications to it:

Only after Professor Dumbledore makes key modifications to the mirror (which has been languishing in the Room of Requirement for a century or so before he brings it out and puts it to work) does it become a superb hiding place, and the final test for the impure of heart. _{^{Pottermore -The Mirror of Erised}}

As far as the magic itself, it's certainly possible that Dumbledore has used something similar to the Evanesco charm, except mirrored (e.g. to make an object appear rather than disappear).

"!evɒnɘƨɔO"