It is not the disk that has the four corners.
The plane is not infinite.
If the plane is not infinite, how can the horizon always stay at eye-level as you claim it does?
Is it’s not infinite then it has edges a finite distance away, and if it has edges a finite distance away, the angle from ones eyes to these will increase as one increases the vertical distance. This is an indisputable a priori fact of geometry, and it doesn’t depend upon whether o e is talking about point on a flat plane or point on a sphere. That is why ANY OBJECT a FINITE distance away immediately SINKS from view as one goes up. For there to be a perpetual horizons at eye level, there has to be MORE OF THE SURFACE coming into view as one ascends; if the surface is finite, this is not possible. Are you literally brain damaged that you cannot comprehend this?