  This Letter addresses the first Solar Orbiter (SO) -- Parker Solar Probe
(PSP) quadrature, occurring on January 18, 2021, to investigate the evolution
of solar wind from the extended corona to the inner heliosphere. Assuming
ballistic propagation, the same plasma volume observed remotely in corona at
altitudes between 3.5 and 6.3 solar radii above the solar limb with the Metis
coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing the
local properties of the solar wind to be linked to the coronal source region
from where it originated. Thanks to the close approach of PSP to the Sun and
the simultaneous Metis observation of the solar corona, the flow-aligned
magnetic field and the bulk kinetic energy flux density can be empirically
inferred along the coronal current sheet with an unprecedented accuracy,
allowing in particular estimation of the Alfv\'en radius at 8.7 solar radii
during the time of this event. This is thus the very first study of the same
solar wind plasma as it expands from the sub-Alfv\'enic solar corona to just
above the Alfv\'en surface.
