FOM: As to D.Hilbert's solution of Waring's Problem

[Alexander Zenkin]

Dear all,

    As is known, David Hilbert was a scientist of genius who enriched
the Mathematics of the XX Century by a lot of outstanding achievements.
Many years ago, I have read somewhere (unfortunately, I can't recall
where) that D.Hilbert himself, by his own confession, appreciated, most
of all his results, the complete solution (obtained in 1909) of the
famous Waring Problem (formulated in 1770) in Number Theory.
  Is it so? And where could that be written?
  Any comments (expecially electronic citations and references) are
welcome.

  Thanks in advance.

Alexander Zenkin