You shouldn't have bothered with calibration weight of 100g. Why? Because your scale range is 1-100g! Your typical sample, however, is on the order of grams to 10s of grams.
You want to calibrate it using the following:
one US nickel and one US dollar (paper).
The first weighs 5 grams and the second 1 gram. Two nickels are 10 grams.
This should bracket nicely the typical range for small sample weight measuring.
Coin weights from the US Mint:
Cent - 2.5 grams
Nickel - 5 grams
Dime - 2.27 grams (~2.3 g)
Quarter - 5.67 grams
Half Dollar - 11.34 grams
These will serve as surprisingly accurate and cheap calibration set for your pocket scale. You want to BRACKET your desired sample weight, calibrating at two points, not one. You can't assume that the scale is linearly accurate over the entire effective weight range. You can try a three point check (bracket the range close to your desired weight and check the third point, close to your mass goal.
For a 5 gram sample, try 2.5 and 7.5g for your calibration points, and 5g for your check point.
For the OCD crowd, you may want to do your measurements in a room with no open windows, fans or air ventilation running, to avoid air disturbance over your sensitive pocket scale.
Nice that it as a 'tare' function, so that you can 'zero-out' the mass of your weighing paper (this is what you should invest in, not the large calibration weight), and ladle your tea directly onto the weighing paper on the scale.
Weighing paper/boats/glassine dishes (all cheap)
http://www.emsdiasum.com/microscopy/pro ... ghing.aspx
The weighing paper will need to be folded into quarters and then opened, to provide an angled surface that keeps your tea from sliding off the otherwise flat sheet.
PS: A hundredth of a gram difference in weighing out your tea isn't going to make a doodle worth of difference in the infusion quality outcome, anyway, because there is uncertainty associated with infusion vessel wall heat capacity and diffusion rate, infusion mixing dynamics, tea leaf age and quality, and temperature measurement.
