  The ${}^{11}$B NMR spectra in polycrystalline MgB$_2$ were measured for
several magnetic fields (1.97 T and 3.15 T) as a function of temperature from 5
K to 40 K. The composite spectra in the superconducting state can be understood
in terms of anisotropy of the upper critical field, $\gamma_{H}$, which is
determined to be 5.4 at low temperature. Using Brandt's algorithm\cite{Brandt}
the full spectrum, including satellites, was simulated for the temperature 8 K
and a magnetic field of 1.97 T. The penetration depth $\lambda$ was determined
to be $1,152\pm50$ {\AA}, and the anisotropy of the penetration depth,
$\gamma_{\lambda}$, was estimated to be close to one at low temperature.
Therefore, our findings establish that there are two different anisotropies for
upper critical field and penetration depth at low temperatures.
