  Let $R_j$ denote the $j^{\text{th}}$ Riesz transform on $\mathbb{R}^n$. We
prove that there exists an absolute constant $C>0$ such that \begin{align*}
  |\{|R_jf|>\lambda\}|\leq
C\left(\frac{1}{\lambda}\|f\|_{L^1(\mathbb{R}^n)}+\sup_{\nu}
|\{|R_j\nu|>\lambda\}|\right) \end{align*} for any $\lambda>0$ and $f \in
L^1(\mathbb{R}^n)$, where the above supremum is taken over measures of the form
$\nu=\sum_{k=1}^Na_k\delta_{c_k}$ for $N \in \mathbb{N}$, $c_k \in
\mathbb{R}^n$, and $a_k \in \mathbb{R}^+$ with $\sum_{k=1}^N a_k \leq
16\|f\|_{L^1(\mathbb{R}^n)}$. This shows that to establish dimensional
estimates for the weak-type $(1,1)$ inequality for the Riesz tranforms it
suffices to study the corresponding weak-type inequality for Riesz transforms
applied to a finite linear combination of Dirac masses. We use this fact to
give a new proof of the best known dimensional upper bound, while our reduction
result also applies to a more general class of Calder\'on-Zygmund operators.
