Full Idea
The best known axiomatization of PL is Whitehead/Russell. There are four axioms: (p∨p)→p, q→(p∨q), (p→q)→(q∨p), and (q→r)→((p∨q)→(p∨r)), plus Substitution and Modus Ponens rules.
Gist of Idea
The best known axiomatization of PL is Whitehead/Russell, with four axioms and two rules
Source
report of B Russell/AN Whitehead (Principia Mathematica [1913]) by GE Hughes/M Cresswell - An Introduction to Modal Logic Ch.1
Book Reference
Hughes,G./Cresswell,M.: 'An Introduction to Modal Logic' [Methuen 1972], p.17