  We use gravitational lensing of the cosmic microwave background (CMB) to
measure the mass of the most distant blindly-selected sample of galaxy clusters
on which a lensing measurement has been performed to date. In CMB data from the
the Atacama Cosmology Telescope (ACT) and the Planck satellite, we detect the
stacked lensing effect from 677 near-infrared-selected galaxy clusters from the
Massive and Distant Clusters of WISE Survey (MaDCoWS), which have a mean
redshift of $ \langle z \rangle = 1.08$. There are no current optical weak
lensing measurements of clusters that match the distance and average mass of
this sample. We detect the lensing signal with a significance of $4.2 \sigma$.
We model the signal with a halo model framework to find the mean mass of the
population from which these clusters are drawn. Assuming that the clusters
follow Navarro-Frenk-White density profiles, we infer a mean mass of $\langle
M_{500c}\rangle = \left(1.7 \pm 0.4 \right)\times10^{14}\,\mathrm{M}_\odot$. We
consider systematic uncertainties from cluster redshift errors, centering
errors, and the shape of the NFW profile. These are all smaller than 30% of our
reported uncertainty. This work highlights the potential of CMB lensing to
enable cosmological constraints from the abundance of distant clusters
populating ever larger volumes of the observable Universe, beyond the
capabilities of optical weak lensing measurements.
