Table 1

texPreview( obj = knitr::kable(mtcars,'latex'))

Table 2

tab='
\\begin{tabular}{llr}
\\hline
\\multicolumn{2}{c}{Item} \\\\
\\cline{1-2}
Animal    & Description & Price (\\$) \\\\
\\hline
Gnat      & per gram    & 13.65      \\\\
          & each        & 0.01       \\\\
Gnu       & stuffed     & 92.50      \\\\
Emu       & stuffed     & 33.33      \\\\
Armadillo & frozen      & 8.99       \\\\
\\hline
\\end{tabular}'

texPreview(obj = tab)