STL map with custom class comparator not working

I have a map which has a class as key.

In this class I overloaded the < operator, I read here that the map will automatically use that for comparison and sorting.

I get the following error when compiling:

Error 1 error C2664: 'std::pair::pair(const std::pair &)' : cannot convert argument 1 from 'Position' to 'Position *const &' e:\program files\visual studio 2013 ultimate\vc\include\xmemory0

I don't get what that really means or how I can avoid it. It doesn't highlight anything in my code either.

Here is my code, my class is coordinates, I want them to be sorted from left to right and top to bottom, but the logic isn't the problem here.

There's obviously more stuff in the Position files, but I think these are the relevant parts.

main.cpp

int main()
{
  std::map<Position*, int> karte;
  Position p1;
  p1.setX(0);
  p1.setY(0);

  Position p2;
  p2.setX(0);
  p2.setY(1);

  Position p3;
  p3.setX(1);
  p3.setY(0);

  Position p4;
  p4.setX(1);
  p4.setY(1);

  karte.emplace(p1, 1);
  karte.emplace(p2, 2);
  karte.emplace(p3, 3);
  karte.emplace(p4, 4);

  for (auto& x : karte)
  {
    std::cout << x.first->toString() << ": " << x.second << std::endl;
  }
  return 0;
}

Position.h

bool operator<(const Position&) const;

Position.cpp

bool Position::operator<(const Position &position) const
{
  if ((x_ < position.x_) && (y_ == position.y_))
  {
    return true;
  }
  if (x_ > position.x_ && y_ < position.y_)
  {
    return true;
  }
  if (x_ == position.x_ && y_ < position.y_)
  {
    return true;
  }
  else
  {
    return false;
  }
}