It’s not going to work, whichever way you slice it.
First off, the embalming process, now rather common in many parts of the world, will kill you, but lets say they forget that bit, or you somehow miraculously survive it…
Next problem: the coffin lid is screwed down - even an ordinary timber coffin is going to be very hard to break out of - if you had some room to take a run or swing at it, you might be able to kick the lid off, but you don’t have much room at all and even if you did, you can’t kick the lid off because there’s a ton of dirt stacked on it. Oh, the lid is probably padded a bit too, which doesn’t help. Or maybe the coffin is actually made of stainless steel or lined with lead, in which case you’re screwed.
No matter; suppose you somehow manage to break a hole in the lid; your next trouble is actually a couple of simultaneous problems, namely:
-You need to move from a cramped, horizontal space into a vertical tunnel, through a hole in the coffin lid that is large enough to let you turn the corner, but small enough that the soil above doesn’t just trickle in and fill the coffin around you.
-You need to dig the tunnel up to the surface and you need somewhere to put the spoil you’re digging out.
If the soil is loosely compacted and dry, digging will be easier, except that it will tend to just crumble in on you and smother you
If the soil is damp clay, it’s less likely to collapse in on you, but it will be much harder to dig and to transport back to the foot of the coffin (the only place you’ve got to put it).
Never mind though, let’s suppose you manage to get started tunnelling upward, somehow. Now you’ve only got to worry about six teeny tiny problems:
[ul][li]You won’t be able to pack the spoil below you as tightly as it was when you dug it out, so your tunnel can only get smaller as you move upwards[/li][li]If the fill is at all loose, it will settle about you and trap you anyway[/li][li]Your oxygen supply is limited.[/li][li]A few short hours ago, you were mistaken for a dead person, so you’re not exactly on top physical form[/li][li]It’s completely and utterly dark; come to think of it, that is a problem for every other stage in the process[/li]Even if you do somehow manage to claw your way to the surface, you’re going to look a real mess; filthy, bruised, bleeding, gaunt, clammy with sweat, wearing tattered clothes and probably unable to speak much more than moans and croaks; the moment you get your head and maybe one grasping arm clear of the surface, some bystander (preconditioned by movies such as Dawn of the Dead etc) is quite likely to freak out and beat the fuck out of you with a shovel.[/ul]