# How does one correctly scale tabu (not tabular)?

Can someone explain the (what is to me) weird behavior of adjustbox in the second and third cases below?

Why is it that all three cases produce different results?

\documentclass{article}

\usepackage{tabu}
\usepackage{booktabs}

\begin{document}

\centering

With c''.
\vspace{1ex}

%
\begin{tabu}{c}
\toprule
\\
Some reasonably, very much so, long text.
\\
\bottomrule
\end{tabu}
%

\vspace{3ex}

With X[c]''.
\vspace{1ex}

%
\begin{tabu}{X[c]}
\toprule
\\
Some reasonably, very much so, long text.
\\
\bottomrule
\end{tabu}
%

\vspace{3ex}

With to 7em'' and X[c]''.
\vspace{1ex}

%
\begin{tabu} to 7em {X[c]}
\toprule
\\
Some reasonably, very much so, long text.
\\
\bottomrule
\end{tabu}
%

\end{document}

Please mind that the text that seems to title each table is not actually a caption (trying not to confuse people with how a \caption would scale).

• (i) use adjustbox for set tables width is not good idea, (ii) be watchful with use of tabu, it is buggy and not maintained. Nov 14 '17 at 7:45
• Because of your comment, I posted a follow-up question, in case you'd be interested in providing more details. tex.stackexchange.com/questions/401353/…
– dow
Nov 14 '17 at 22:40