  Yu and Littlejohn recently studied in arXiv:1104.1499 some asymptotics of
Wigner symbols with some small and large angular momenta. They found that in
this regime the essential information is captured by the geometry of a
tetrahedron, and gave new formulae for 9j, 12j and 15j-symbols. We present here
an alternative derivation which leads to a simpler formula, based on the use of
the Ponzano-Regge formula for the relevant tetrahedron. The approach is
generalized to Wigner 3nj-symbols with some large and small angular momenta,
where more than one tetrahedron is needed, leading to new asymptotics for
Wigner 3nj-symbols. As an illustration, we present 15j-symbols with one, two
and four small angular momenta, and give an alternative formula to Yu's recent
15j-symbol with three small spins.
