We report the identification of the M9 dwarf SDSS J000649.16 - 085246.3 as a spectral binary and radial velocity variable with components straddling the hydrogen burning mass limit . Low-resolution near-infrared spectroscopy reveals spectral features indicative of a T dwarf companion , and spectral template fitting yields component types of M8.5 \pm 0.5 and T5 \pm 1 . High-resolution near-infrared spectroscopy with Keck/NIRSPEC reveals pronounced radial velocity variations with a semi-amplitude of 8.2 \pm 0.4 km s ^ { -1 } . From these we determine an orbital period of 147.6 \pm 1.5 days and eccentricity of 0.10 \pm 0.07 , making SDSS J0006 - 0852AB the third tightest very low mass binary known . This system is also found to have a common proper motion companion , the inactive M7 dwarf LP 704-48 , at a projected separation of 820 \pm 120 AU . The lack of H \alpha emission in both M dwarf components indicates that this system is relatively old , as confirmed by evolutionary model analysis of the tight binary . LP 704-48/SDSS J0006 - 0852AB is the lowest-mass confirmed triple identified to date , and one of only seven candidate and confirmed triples with total masses below 0.3 M _ { \sun } currently known . We show that current star and brown dwarf formation models can not produce triple systems like LP 704-48/SDSS J0006 - 0852AB , and we rule out Kozai-Lidov perturbations and tidal circularization as a viable mechanism to shrink the inner orbit . The similarities between this system and the recently uncovered low-mass eclipsing triples NLTT 41135AB/41136 and LHS 6343ABC suggest that substellar tertiaries may be common in wide M dwarf pairs .