What is the only self-contained direction-seeking instrument found in the cockpit?

The magnetic compass is the only self-contained direction-seeking instrument found in the cockpit because it does not require any external power source or electronic components to function. It operates based on the Earth's magnetic field, providing pilots with a reliable indication of their heading. Unlike other instruments, the compass does not rely on electricity or other outside inputs, making it a fundamental tool for navigation.

The heading indicator, while used for determining direction, is not self-contained as it requires electrical power and is typically dependent on a reference provided by the magnetic compass. The Electronic Flight Instrument System (EFIS) relies on various sensors and components to display flight information, thus not qualifying as self-contained. The artificial horizon, or attitude indicator, is designed to show the aircraft's orientation relative to the horizon, but it too requires electronic inputs and is not a primary direction-seeking tool. Therefore, the magnetic compass stands out as the only self-reliant instrument for navigation in the cockpit.