Wiglaff borrows a spear and starts poking the nearest tiles with the butt, to see if there is any sign of give. He gives the rest of the party time to back up before he gets started.
If he finds any sign of give or wobble, or anything weird happens, he stops. Otherwise, he'll poke out as far as he can from the doorway.
If the poking reveals nothing, he'll cast detect magic and scan the room (including floor, walls, ceiling).
Assuming nothing happens or is discovered, he'll attempt to cross the room. Given the available numbers, would it be possible to step/hop from number to number in a pattern, e.g. 1, 2, 3, ...? If so, he'll try that. If not, he just goes across, but in a random fashion, not a straight path. E.g. start on one number, take a big step across several tiles to another number, then hop right, forward, hop left, etc.
[f=32]Wiglaff the Elf, F3/MU2
(M 12", AC 9, HD 4+1, hp 14/14, N) cloak of elvenkind
, battle-axe; light, colour spray
[f=47]Wilibald "Willie" Whitfoot, F1/T1
(M 12", AC 6, HD 1+2, hp 9/9, L) gambeson+helm, shield+warhammer[/f]