  Three simple $7-, (7+3)-, 10-$parametric trial functions for the ${\rm
H}_3^+$ molecular ion are presented. Each of them provides subsequently the
most accurate approximation for the Born-Oppenheimer ground state energy among
several-parametric trial functions. These trial functions are chosen following
a criterion of physical adequacy and includes the electronic correlation in the
exponential form $\sim\exp{(\gamma r_{12})}$, where $\gamma$ is a variational
parameter. The Born-Oppenheimer energy is found to be $E=-1.340 34, -1.340 73,
-1.341 59$\,a.u., respectively, for optimal equilateral triangular
configuration of protons with the equilibrium interproton distance
$R=1.65$\,a.u. The variational energy agrees in three significant digits (s.d.)
with most accurate results available at present as well as for major
expectation values.
