|Edward Norton Lorenz derived his equations from Saltzman's free convection equations,
simplified as to get the essence of the non-periodic behaviour noticed about their variations.
Written in 1962 and published in 1963, his original paper contains all the main characters
of the chaos theory - although this theory didn't exist at the time : the use of a computer,
simplifications of the equations, sensivity to initial conditions, use of Poincaré's map, etc ...
Original Lorenz paper - Deterministic nonperiodic flow (1963) - PDF