Before the 1761 transit, what was our best estimate of the distance to the Sun?
Aristaurus gives a calculation which would result in a value for the Earth-Sun distance  of about 0.016-0.065AU, clearly that's a long way out. The true value is 1.00 AU
Archimedes gives a value that would correspond to 0.43AU, other Ancient authors gave a range of values, all less than 0.5AU and many were close to Aristaurus's value.  So among ancient writers, all we can really say is that &quot;They had no idea how far the sun was&quot;.
Kepler and his laws of planetary motion could show that values of 0.02au were far too small (since then a very significant parallax would be visible in venus) but couldn't say with precision how far out.
In the 17th century, telescopic measurements of the Earth-Sun-Moon angle allowed for Aristaurus's method to be used with greater precision and yielded values of 0.5 or more
Huygens made a number of assumptions on the size of the planets and came up with a very good value of 1.068AU,  but his reasoning was faulty.  This value is more luck than good maths. However, Cassini used observations of Martian parallax (and a good estimate of the size of the Earth) to get a well-calcuated value of 0.925AU
This was the best estimate prior to the measurement using transit of Venus.