Who was the Provisional President of the Constituent Assembly before Dr. Rajendra Prasad took over?

Dr. Sachchidananda Sinha was elected as the temporary President of the Constituent Assembly during its first meeting on December 9, 1946, following the French practice of appointing the oldest member. While Dr. B.R. Ambedkar is a prominent figure often associated with leadership, he served as the Chairman of the Drafting Committee rather than the presiding officer of the Assembly. This question tests the historical timeline and initial leadership structure of the Constituent Assembly.