uses System.Variants,
  System.Generics.Collections;

var
  List: TList<Variant>;
  Number: Variant;
begin
  //no common numeric base type;
  //Variant holds a number of any kind
  List := TList<Variant>.Create;
  List.Add(Byte(42));
  List.Add(512); //Integer
  List.Add(SmallInt(1024));
  List.Add(Int64(777));
  List.Add(3.14); //Double

  for Number in List do
    WriteLn(VarToStr(Number));
end.