Otto Rössler 1976 — simplest autonomous 3D chaotic flow, prototype of funnel chaos
The Rössler system:
models a chemical oscillator. At c≈5.7 it undergoes period-doubling to chaos via the Feigenbaum route. The attractor has a funnel shape: the trajectory spirals out in the xy-plane, then is reset by the z-spike.
Lyapunov exponent λ₁ ≈ 0.07 at standard params — weak but genuine chaos.