...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::units::si::constants::codata::BOOST_UNITS_PHYSICAL_CONSTANT — CODATA recommended values of the fundamental physical constants: NIST SP 961.
// In header: <boost/units/systems/si/codata/tau_constants.hpp>
BOOST_UNITS_PHYSICAL_CONSTANT(m_tau, quantity< mass >,
3.16777e-27 * kilograms, 5.2e-31 * kilograms);