I know this may sound incredibly crude, but we actually used to put a penny (weighs about 3 grams) on the head shell of a turntable to add effective mass to the tonearm when needed to match the phono cartridge compliance (How do I choose a turntable?).  Of course, this was suboptimal and more of an interim solution until the proper tonearm for the phono cartridge of choice was found, but it worked amazingly well.  So well that some manufacturers offered weight kits for their head shells for this purpose (see photo above).

The trackability of a cartridge is related to the mechanical parameters of the tonearm and stylus assembly. Adding weight to the headshell, and adjusting the counterweight to compensate, increases the effective mass of the tonearm and reduces its resonant frequency. If the resonant frequency is excessively high (e.g., 15-20 Hz, as measured by a test record), the increased mass may improve sound quality by moving the resonance out of the audible range.