SSS parameters from Renderman Manual

refraction for twelve materials from [Jensen01]:

                 albedo              dmfp                ior
   apple        0.846 0.841 0.528    6.96  6.40  1.90   1.3
   chicken1     0.314 0.156 0.126   11.61  3.88  1.75   1.3
   chicken2     0.321 0.160 0.108    9.44  3.35  1.79   1.3
   cream        0.976 0.900 0.725   15.03  4.66  2.54   1.3
   ketchup      0.164 0.006 0.002    4.76  0.58  0.39   1.3
   marble       0.830 0.791 0.753    8.51  5.57  3.95   1.5
   potato       0.764 0.613 0.213   14.27  7.23  2.04   1.3
   skimmilk     0.815 0.813 0.682   18.42 10.44  3.50   1.3
   skin1        0.436 0.227 0.131    3.67  1.37  0.68   1.3
   skin2        0.623 0.433 0.343    4.82  1.69  1.09   1.3
   spectralon   1.000 1.000 1.000     inf   inf   inf   1.3
   wholemilk    0.908 0.881 0.759   10.90  6.58  2.51   1.3