Changing size of bullets in beamer (recommended solution causes error) [duplicate]

Question

I can customise Beamer to use circles instead of triangles for bullets like so:

\documentclass{beamer}

\setbeamertemplate{itemize item}[circle]

\begin{document}

\begin{frame}{Title 1}
\begin{itemize}
  \item{a bullet}
  \item{another bullet}
\end{itemize}
\end{frame}

\end{document}

According to the Beamer user guide. p. 10, I should be able to control the size of the circle by changing

\setbeamertemplate{itemize item}[circle]

to

\setbeamertemplate{itemize item}[circle]{3pt}

However, when I make this change, I get an error:

! LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.3 \setbeamertemplate{itemize item}[circle]{3
                                              pt}
? 

I have tried both xetex and pdflatex, with the same result. Here's some version information:

This is XeTeX, Version 3.141592653-2.6-0.999994 (Web2C 2022/nixos.org) (preloaded format=xelatex)
 restricted \write18 enabled.
entering extended mode
(./amy.tex
LaTeX2e <2022-11-01> patch level 1
L3 programming layer <2022-12-17>
(/nix/store/p421m408x2ksfl7xx159ppvgcmr8lg6q-texlive-combined-full-2022.2022122
7/share/texmf/tex/latex/beamer/beamer.cls
Document Class: beamer 2022/09/13 v3.68 A class for typesetting presentations

Answer 1

The example in the manual is slightly misleading, as it does not provide the full code to make that example work in that page. If you look at page 168 then you see that there is a \defbeamertemplate statement before, and that this is specific for the square template.

For cirlces you can define your own template for bigger circles. For example:

\documentclass{beamer}

\defbeamertemplate{itemize item}{bigcircle}{\usebeamerfont*{itemize item}\raise-1.5pt\hbox{\huge\donotcoloroutermaths$\bullet$}}


\begin{document}

\begin{frame}{Title 1}
\setbeamertemplate{itemize item}[circle]
\begin{itemize}
  \item{a bullet}
  \item{another bullet}
\end{itemize}
\setbeamertemplate{itemize item}[bigcircle]
\begin{itemize}
  \item{a bullet}
  \item{another bullet}
\end{itemize}

\end{frame}

\end{document}

Answer 2

Page 10 does not say that the itemize item template takes such an additional argument. It only shows that some templates can use such an additional argument. itemize item is not a template which was defined with such an additional argument.

To avoid further users getting confused over this, the section in beamer user guide now reads as

Instead you can redefine the template and change the size of the bullet:

\documentclass{beamer}

\setbeamertemplate{itemize item}{\usebeamerfont*{itemize item}\raise-2pt\hbox{\donotcoloroutermaths\scalebox{2}{$\bullet$}}}

\begin{document}

\begin{frame}{Title 1}
\begin{itemize}
  \item{a bullet}
  \item{another bullet}
\end{itemize}
\end{frame}

\end{document}