Highest point on a Rhino curve or surface

I have a need to find the highest point on a curve or surface with the convex side up. Any idea how it could be done?

On a surface make a Silhouette in an elevation view then snap using Quad on the resulting curve. For a curve is the current Cplane is in elevation relative to the high point, then Quad will find X and Y direction extremes. - Pascal Rhino Newsgroup