Death Mountain Ascent
Death Mountain Ascent (commonly shortened to DMA) is a way to enter Death Mountain using Out of Bounds. This allows you to skip the Power Gloves, which you'd ordinarily need to access the cave to take you up Death Mountain.
Wall Clipping with Boots
It's possible to enter Death Mountain by using the boots to clip into a diagonal wall on the overworld and then activating an upwards teleport to place Link on a different screen. From here you can transition right to Death Mountain.
Clipping through Slope
There are multiple ways to clip through diagonal edge, the easiest way is to pressor and press at the same time while holding the sword up.
Starting point and teleport
There are multiple starting points in each edge that will work.
Here are two starting point that work.
You can see a "hole" in the grass under Link's shadow for the first one.
Then you must do 8input, you can count or just use visual cue for stopping that
Here you can see for example only 1 pixel of link's feet shadow that go out.
When you reach that, releasethen hold .
Entering the cave
Move up and right a bit, then enter the right screen.
You are at the bottom on death mountain, but you will not see the map properly
Don't try to enter the cave immediately, the game will have trouble making the black hole closing transition, at best it will take forever, or just crash.
You need to make the camera scroll up (move up and down), you will start seeing the squirrel and boulders but not the entrance. You can try to enter the cave now, It should be fine.
SMV and video
You can find a SMV here : Easy DMA.smv