Is this possible?

[krk]

damn it you won't grow alot from bodyweight exercises... you will if you are a complete novice and it will be slight... then once you are over it YOU WON'T GROW! repeat YOU WON'T GROW! try adding more reps or less YOU WON'T GROW! period! repeat YOU WON'T GROW!

Eric Dickerson might disagree with you.

 

[Papa Lion]

Nope, you need to eat more to gain mass.

Although pullups and pushups could add some muscle, I would just do maby 20 of each per day, throw in some bodyweight squats, bearwalk and crabwalk, add in the plank and add lunges and you have a decent bodyweight workout.

I started my gf on more than 20 pushups... though it's not every day!! it's still extremely light!! and during season when I coach... my HS wrestlers are doing 3 or four times that in their first workout!! and for some I really their "first" workout!!

 

[Papa Lion]

ohh an since you decided to throw a backpack into it then yes those exercises will help you grow since I'm assuming you don't have much training exp!! also try throwing the back pack on while you do your pushups and grab a few chairs and and put your hands on one each and your feet on the other this allows you to go a lil deeper!!

 

[StuWard]

As long as you respect the overload principle and keep increasing the load you can make gains. There are lots of ways to increase the loads and increase the range of motion on body weight exercises. If you keep the load constant and keep adding reps you will be wasting your time. Here's a couple of web sites that may give you some ideas:
http://www.elitefts.com/documents/body_barbell.htm
http://www.drillsandskills.com/skills/index
http://www.dragondoor.com/articler/mode2/Workouts
http://bodyweightculture.com/index.php