  We present an analytic calculation of the first transcendental in
phi^4-Theory that is not of the form zeta(2n+1). It is encountered at 6 loops
and known to be a weight 8 double sum. Here it is obtained by reducing multiple
zeta values of depth <= 4. We give a closed expression in terms of a
zeta-related sum for a family of diagrams that entails a class of physical
graphs. We confirm that this class produces multiple zeta values of weights
equal to the crossing numbers of the related knots.
