Query: Name of French Explorer

[Koontz John E]

I seem to recall reading somewhere of a French explorer who was an early
visitor to the Dakota, probably the Mille Lacs Santee villages, and who
has something of a reputation among commentators as being unreliable.  I
am trying to remember his name.  One of his purported stretches, as I
recall, was claiming (to Louis XIV) that the Dakota word for 'sun', as in
'Louis the Sun King' was "Louis."  Of course, apparently unbeknownst to
the amused commentators, the Dakota word for 'sun' (and 'moon') actually
is wi, which is a credible match for Louis [lwi].  Does anyone remember
this annecdote or the French explorer's name?

John