While playing Portal 2 I encountered several drawings on the walls:

Something about someone getting shot, companion cubes, people choking on poisonous gas and Chell doing nasty things to GLaDOS.

Something about Schrödinger’s cat (?) and mathematics that don’t make any sense to me.

“The bell invites, hear the turret, for it is knell. That summons to heaven or to hell.” Apparently this is a Macbeth quote:

"I go, and it is done; the bell invites me. Hear it not, Duncan, for it is a knell That summons thee to heaven or to hell."

How it relates to the game however is a mystery to me. So does anyone know what the story behind them is and what they mean?