Corrections, Built Before Machines

This is the public corrections record for the Built Before Machines channel. Every episode's sources are listed in its description.

When we get something wrong and someone shows us a better source, the correction is logged here with the date, the episode, what we said, what is right, and the source that showed it. Important corrections are also read on screen in an upcoming episode.

Nothing is quietly deleted. If a correction is itself corrected, the old line stays, struck through, with the new one below it.

How to send a correction

Reply to the pinned comment under the episode. Give the exact page or line of a published source.

The log

Newest first. A struck line was later corrected by the row below it.
No.	Date	Episode	What we said	What is right	Source
No. 1	2026-09-15	12 Metres of Fall Across 50 Kilometres	At 20:51 the narration says nobody has ever found a Roman levelling instrument, and the Still unsettled card says none has been excavated.	That is broader than our sources. No excavated dioptra, water level or chorobates is known, and Lewis says no dioptra has yet been found, or at least identified. Romans also used a plain A-frame builder's level with a plumb line, and we have not confirmed that no example survives.	M. J. T. Lewis, Surveying Instruments of Greece and Rome, Cambridge 2001, chapter 3 summary