Who was the first to compile works on the principles of Islamic jurisprudence (Usul al-Fiqh)?

It has been said that the first to compile works on the science of Usul al-Fiqh (principles of Islamic jurisprudence) and establish its rules were Abu Yusuf and Muhammad, the two students of Abu Hanifa, or Abu Yusuf alone, or Abu Hanifa in a book he named "Kitab al-Ra'y" (The Book of Opinion). However, nothing of that has reached us. What is widely known is that the first to write independently on this science was Imam al-Shafi'i in his book "Al-Risala" (The Epistle).