What is the minimum obligatory duration required for the Final Sitting (al-Qa'dah al-Akhirah)?

The Pillars of Prayer Part 3: Sittings and Final Exit

• Sitting for exactly one minute.
• Sitting for the duration of reciting the complete Tashahhud (Attahiyyat).
• Sitting for the duration of reciting the Surah al-Fatihah.
• Just touching the ground with the buttocks and standing up.