Weekly Gold/Silver Ratio for the past 25 years.
http://www.sharelynx.com/charts/AuAG.gif
shows ratio below (gold above) 25-1 since 1976, except for the brief bubble in 1980, when it reached 16-1.
I found another chart, purporting to show prices back to 1400, which showed a ratio around 15 or 20-1, UP TO ABOUT 1824, after which gold has been almost always at 20-1, up to nearly 100-1, as I read that chart.
http://www.eh.net/hmit/goldprice/answer.php
if you run it for 1776 to 1998, shows the ratio around 16-1 until the 1880s, after which it stays above 20-1, almost all the time, and reaches into the 90-1 area at some times.