Grimrock

I'm running back through all the little things I skipped over on my first play through, and there is one puzzle in the first level of the inside cemetery (ok, 2nd level) that seems improbable for me to complete:

There is a cubbie hole over a force field with a riddle saying:

"With icicles from beneath, I strike at thee."

Which to me means to cast 'Ice shards' at the cubbie hole, but I don't have the ability to cast that spell. I've tried putting several "cold" related odds and ends inside, but to no avail. Any hints?

It isn't a spell (I thought the same at first)

Hint More specific

Thanks!