How to visualize axis-aligned boxes with ParaView

Question

I would like to visualize a number of axis-aligned bounding boxes in ParaView. I will create an unstructured grid and insert vtkVoxel cells in there. How many points should each voxel be associated with? Since the documentation says voxels are efficient in storage, I thought two corners would be enough, but this post, for example, seems to be setting 8 for each of them. I was not able to get anything from the documentation either.