  This article reports quasi-continuous transiting events towards WD 1054-226
at d=36.2 pc and V=16.0 mag, based on simultaneous, high-cadence,
multi-wavelength imaging photometry using ULTRACAM over 18 nights from 2019 to
2020 March. The predominant period is 25.02 h, and corresponds to a circular
orbit with blackbody Teq = 323 K, where a planetary surface can nominally
support liquid water. The light curves reveal remarkable night-to-night
similarity, with changes on longer timescales, and lack any transit-free
segments of unocculted starlight. The most pronounced dimming components occur
every 23.1 min -- exactly the 65th harmonic of the fundamental period -- with
depths of up to several per cent, and no evident color dependence. Myriad
additional harmonics are present, as well as at least two transiting features
with independent periods. High-resolution optical spectra are consistent with
stable, photospheric absorption by multiple, refractory metal species, with no
indication of circumstellar gas. Spitzer observations demonstrate a lack of
detectable dust emission, suggesting that the otherwise hidden circumstellar
disk orbiting WD 1054-226 may be typical of polluted white dwarfs, and only
detected via favorable geometry. Future observations are required to constrain
the orbital eccentricity, but even if periastron is near the Roche limit,
sublimation cannot drive mass loss in refractory parent bodies, and collisional
disintegration is necessary for dust production.
