When you ascend a staircase leading to Arquebald's floor in Old Ebonheart, Guild of Mages, there is a caspering support plank on one of the sides of the staircase. The same is true with the case of the Firewatch, Guild of Mages, where the casper happens on a staircase leading from the teleportation floor to the entrance hall with a Khajiit and the guardian.