2-soliton solution of the KdV equation via Bianchi permutability:

m1= 2 (bounded)
m2= 8 (unbounded)

                12(-8csch[2(x-16t)]^2 - 2sech[x-4t])^2)
u(x,t) =    ------------------------------------------
                    (4coth[2(x-16t)] + 2tanh[x-4t])^2

Time steps: t=-0.5, -0.4, ..., 0, ..., 0.5