Declare an object as an instance of System.Math.

DeclareAsMath.cs

using System;
using System.Linq;
using System.Reflection;


class Program
{
	class MyClass	
	{	
	}	

	static void Main(string[] args)
	{
		var mscorlib = AppDomain.CurrentDomain.GetAssemblies().First(a => a.GetType("System.RuntimeType", false, true) != null);
		var runtimeType = mscorlib.GetType("System.RuntimeType");	


		var handle = runtimeType.GetField("m_handle", BindingFlags.Instance | BindingFlags.NonPublic);

		var mathTable = handle.GetValue(typeof(Math));	
		handle.SetValue(typeof(MyClass), mathTable);	


		var o = new MyClass();
		Console.WriteLine(o.GetType()); // System.Math
	}
}