This is obviously a corrupt form of some common character as the text is using it as a size comparison that readers are expected to understand. I strongly suspect it is just a corrupt form of U+8C4C 豌 (variant form ⿰豆⿱宀外 with 宀 lost). Therefore suggest withdaw or pending.

I agree with Andrew that this character is likely an error of 豌.

The text here is a quote from 本草, as is shown on the previous folio here. Text is similar to 救荒本草 but 「如⿰豆外豆大」is not included.


▲ 救荒本草（明嘉靖34年刊本）卷上之後 folio 23b 24a

The digitalized text of 三農紀 by Beijing Erudition Digital Research Center also gives 豌:


Size comparison with 豌豆 is also common in various 本草 works:


If anyone can access the modern version of 三農紀: 《三农纪校释》农业出版社（1989）, it would be great to check if ⿰豆外 is preserved or corrected to 豌.