L’errore è stato mio, di interpretazione delle tue richieste. Prova questo codice:`\documentclass{book}
\usepackage{rotating,booktabs, multirow,array}
\newcolumntype{P}[1]{>{\centering}p{#1}}
\begin{document}
\begin{sidewaystable}[hp]
\caption{Scheme of the historical phases of colorimetry, vision stages, visual fields with reference to CIE standard systems}
\label{tab1}
\centering
\begin{tabular}{llP{0.2\columnwidth}P{0.2\columnwidth}P{0.2\columnwidth}}\toprule
& & \multicolumn{3}{c}{\textbf{Historic evolvement}} \\\cmidrule{3-5}
& \multirow{5}*{ } & 1\textsuperscript{st} historic phase & 2\textsuperscript{nd} historic phase & 3\textsuperscript{rd} historic phase\tabularnewline
& & \emph{“colour appearance”} & \emph{“colour difference”} & \emph{“colour appearance”}\tabularnewline[2ex]
& & 1\textsuperscript{st} vision stage & 2\textsuperscript{nd} vision stage & 3\textsuperscript{rd} vision stage\tabularnewline
& & \emph{transduction} & \emph{adaptation} & \tabularnewline[2ex]
& & psychophysic system & psychometric system & \dots \tabularnewline\cmidrule{2-5}
\multirow{4}*{field of view\rule{0pt}{3ex}}& \multirow{2}*{foveal vision} & CIE 1931 std observer & CIELUV/LAB systems & CIECAM Retinex \tabularnewline
& &\textsc{Judd-Vos} observer \tabularnewline[2ex]
& extra-foveal vision & CIE1 964 supplemental observer & CIELUV/LAB systems & \dots \tabularnewline\bottomrule
\end{tabular}
\end{sidewaystable}
\end{document}` Nel [tt]\rule{0pt}{3ex}[/tt] aggiusta il coefficiente 3 con opportuni decimali in più o in meno.