Dragon Magazine #97 addresses this for AD&D
On page 10 of the May, 1985 issue of Dragon Magazine is an article by Stephen Inniss entitled "Sticks, stones, and bones: Weapons to use when the enemy swipes your sword."
The article covers the use of many improvised weapons including rocks ranging from small (with a weight of 2, meaning 0.2 pounds) through very large rocks weighing 15 pounds or more. A medium rock by this article's estimation weighs half a pound and does 1-2 damage against S and M size opponents and 1 against L opponents. A large rock, weighing 3.5 pounds, does 1-3/1-2. The article suggests a rate of fire of 2 for medium rocks and 1 for large and limits damage bonuses (though not to hit bonuses):
The maximum allowable damage bonus is +1 for small rocks, +2 for
medium-sized rocks, +3 for large rocks, and +4 for very large rocks, whether the bonus is due to strength, skill, magic, or a combination of these factors.
However, "to hit" figures are not subject to any such restrictions.
The article categorizes the suitability of non-weapon objects as weapons into classes ranging from an actual weapon, to "same form, but different purpose" (class 1, -1 to hit penalty) down to "poor design for combat use" (class 3, -3 to hit penalty).
Specially selected stones of an ovoid or spherical shape may be classified as actual weapons, ordinary rocks of good material but not carefully sorted qualify as class 1, those chosen in greater haste or from less desirable material are class 2, and those merely snatched up or chosen from very poorly shaped material are class 3.
Large rocks have a range of 1/2 S, 1 M, 1 1/2 L and use the same armor class adjustments as a hurled hammer.
Medium rocks have a range of 1 S, 2 M, and 3 L and use roughly the same armor class adjustments as a sling stone.
The article covers a wide range of objects and also hot liquids such as boiling water and irritants such as sand and lye.
Special tip: a kettle of hot syrup is a dangerous weapon!