  For the simplest minisuperspace model based on a homogeneous, isotropic
metric and a minimally coupled scalar field we derive analytic expressions for
the caustic which separates Euklidean and Minkowskian region and its breakdown
value $\p_*$. This value represents the prediction of the no-boundary wave
function for the scalar field at the beginning of inflation. We use our results
to search for inflationary models which can render the no-boundary wave
function consistent with the requirement of a sufficiently long inflationary
period.
